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UNDERGROUND INTRIGUE: A CONJECTURAL ASSESSMENT OF INCURSION TUNNELS IN A FUTURE NAGORNO-KARABAKH CONFLICT
Posted on August 13, 2014 Karabakh
https://karabakhsecurityanalysis.wordpress.com/2014/08/13/underground-intrigue-a-conjectural-assessment-of-incursion-tunnels-in-a-future-nagorno-karabakh-conflict/
Overview and Background
2014 already appears to be as bloody, if not more so, than previous
years along the front lines of the Nagorno Karabakh conflict. It
seems that every week or two the so-called frozen conflict claims a
new victim - typically a young Armenian or Azerbaijani soldier, but
on occasion an innocent civilian who ended up in the wrong place at
the wrong time. While the majority of the fatal ceasefire violations
occur along the de facto Nagorno Karabakh Republic - Azerbaijani line
of contact, they have also broken out along Armenia's northeastern
international border with Azerbaijan. More worrisome still, recent
reports suggest that the violence may also be spreading to Armenia's
southwestern border with Azerbaijan's Nakhchivan exclave.[i]
A plethora of documentaries and articles have sought to capture the
tense atmosphere at the front - with commentators often comparing the
situation to the type of trench warfare that occurred on the Western
Front during World War I.[ii],[iii],[iv] Similar to Verdun, France one
hundred years ago, two entrenched and generally static forces face off
against each other along the Karabakh line of contact. Corroborated by
a casual Google Earth investigation, reports suggest opposing trenches
are, at places, separated by only a few dozen yards. Recent fatalities
also indicate minefields are scattered throughout no-man's-land,
although it's not entirely clear whether these are newly emplaced or
remnants from the hot war that ended in 1994.[v] There are a number
of acute differences between the Karabakh situation and prototypical
trench warfare, however. Perhaps the most obvious is the fact that
the Karabakh conflict no longer includes human wave attacks, although
these suicidal charges did occur in the waning days of the war.
While major offensives no longer seem to be in the offing, at least
in the near term, regional news reports reveal that 'commando raids'
still occur on a frequent basis.[vi] It's difficult to ascertain which
side is responsible for the raids owing to mutual recriminations, but
on the face of it, Azerbaijan seems to have the most to gain from such
provocations considering it's the least satisfied with the status quo.
Nevertheless, it's reasonable to assume the Armenian side also stages
punitive attacks to demonstrate its resolve and military capability.
The situation along the line of contact, therefore, can best be
described as unstable, but with neither side willing to commit to a
major offensive designed to capture territory. However, the purpose
of this article is not to recap the current situation on the ground,
but to focus on another aspect of the Karabakh conflict that doesn't
receive coverage - namely, what's going on underground. In other
words, this paper will explore the use, or non-use, of offensive
incursion tunnels.
Armies have employed tunneling to bypass or undermine fixed defenses
for hundreds if not thousands of years. The Ottoman Turks employed the
technique in an attempt to capture Vienna in the 16th century only
to be thwarted by the city's defenders, who successfully dug what
can best be described as counter-tunnels.[vii] During World War I,
opposing armies hoped tunnels could help break the trench-warfare
stalemate.[viii] Moreover, one should not mistake this tactic to be
some obsolete historical relic, as four North Korean incursion tunnels,
large enough to accommodate an invasion force of thousands, were
discovered in the latter half of the 20th century; and commentators
speculate that there may be dozens more yet to be discovered.[ix],[x]
Even in our back yard, Mexican drug cartels successfully dig secret
tunnels to bypass the heavily fortified and monitored southern
U.S. border.[xi],[xii]
Given the evident utility of tunneling, it's reasonable to ask why
Azerbaijanis or Armenians aren't employing the method to circumvent
or bypass the heavily defended Karabakh line of contact. A more
circumspect individual might caveat the question by further asking
why neither side has reported the use of tunneling, since a fairly
comprehensive, English-language, internet search yields almost no
substantive documentation on the subject - hypothetical or factual
(there admittedly are a few passing references in forums). After
ruminating over the mystery a while, one would likely arrive at one
or several of the following explanations:
(Hypothesis 1) Neither side is able to dig incursion tunnels for
financial or technical reasons.
(Hypothesis 2) The opposing forces deliberately choose not to dig
tunnels despite the fact that they are physically capable of doing so.
(Hypothesis 3) The sides have indeed built secret contingency/incursion
tunnels, which will only be used if/when the conflict reverts to
a hot-war.
(Hypothesis 4) Armenian and Azerbaijani forces actually use tunnels
on a regular basis to stage commando raids, but choose not to release
this information to the press.
Hypothesis 1
In evaluating these four options, it seems the first scenario can be
safely discarded for a number of reasons. Azerbaijan frequently boasts
that its annual defense budget is larger than Armenia's entire state
budget, because of its burgeoning oil industry. This fact alone
indicates the country is financially capable of digging tunnels
only a few hundred yards in length, especially considering precious
instances where less-endowed antagonists were able to afford similar
undertakings, e.g. North Korea. While the Armenian/Karabakh side is
admittedly poorer than its rival, Armenia's annual defense budget
is still ~400 million dollars per year. This figure is more than a
hundred times the amount purportedly needed to build a sophisticated
narcotics tunnel beneath the Mexican-US border.[xiii],[xiv] In other
words, Armenia would only need to devote one or two percent of its
military budget to carry out this type of activity, which is hardly
an insufferable expense.
Technical challenges also fail to satisfactorily explain the apparent
lack underground excavation. While the topography of the line of
contact is indeed rugged and daunting at places, it nevertheless
remains surmountable from an engineering standpoint. An anecdotal
example that reflects this reality is the strategic auto-tunnel that
lies the south of Kelbajar.[xv] From a more macro-scale geological
perspective, much of the line of contact is situated on ground
that is composed of flood plain, alluvial deposits.[xvi] This loose
soil/gravel/stony mixture usually doesn't require dynamite or heavy
equipment to move, which seems evident enough after viewing photos of
existing trenches on the frontline.[xvii] There is one noteworthy
exception to this general rule, however; namely, the east-west
running Murovdag/Mrav mountain range, which consists of harder basalt,
sandstone and limestone. In any case, if the opposing sides wanted
to engage in tunneling, it appears they would be able to do so -
at least for most sections of the front.
Hypothesis 2
The second explanatory hypothesis considers the possibility that
there is a de facto - if not de jure - policy against underground
excavation. There are a number of reasons why a leader might
deliberately choose to forgo the advantages derived from tunneling.
For instance, they may fear a scenario in which the adversary showcases
a discovered tunnel to prove that the other is acting in bad faith
vis-a-vis the ceasefire regime. This theory breaks down under closer
scrutiny, however, because the antagonists, Azerbaijan in particular,
do not appear to be overly fearful of making truculent statements
and carrying out provocative actions. This is best exemplified by
Baku's 2012 decision to free and publically venerate Ramil Safarov,
who brutally murdered an Armenian serviceman during a NATO exercise in
Hungary. This inflammatory action generated nearly universal western
condemnation, yet Azerbaijan adamantly maintains that it was acting
well within its rights. In a similar vein, Baku frequently claims it is
developing and/or possesses the military capability to forcibly resolve
the Karabakh conflict in the event that the ongoing Minsk Group break
down, which could antagonize European and American interlocutors who
repeatedly proclaim that there is no military solution to the Karabakh
issue. Given this behavior, it seems unlikely that Azerbaijan would
shun subterranean activity solely to avoid hypothetical Western
criticism. And even if Armenian forces were to claim that they
located an Azerbaijani incursion tunnel, Baku could always deny any
responsibly or else could call such accusations "lies," which would
serve to ensure that true and accurate revelations get lost in the
broader propaganda war currently being waged between the two countries.
Another factor that may deter political or military commanders from
ordering underground operations is the prospect that such a decision
could needlessly and dangerously destabilize the line of contact,
and, by extension, the status quo. While the current situation on
the front is bloody, it is nevertheless predictable, if not well
managed. After one or two soldiers are killed on one side, several
troops on the opposing side will typically end up getting shot over
the course of the next several days; this cycle then repeats itself on
a periodic basis. Introducing tunneling into the equation, however,
could jeopardize this set pattern by allowing one or both sides to
engage in asymmetrical retaliation. Provided the antagonists are able
to covertly enter enemy territory via incursion tunnels, one side could
swiftly kill a dozen rivals to avenge the death of one of their own.
This in turn may precipitate an escalating response from the enemy
(e.g. heavy artillery), which would set in motion an unexpected and
undesired chain of events that could easily spiral out of control.
Thus, since neither side is interested in an accidental war, it's
possible they have arrived at some sort of de facto or gentlemen's
agreement to avoid underground warfare altogether.
Hypothesis 3
While the preceding theories explain why incursion tunnels haven't
been constructed along the line of contact, it's entirely conceivable
that we (the public) are unaware of existing tunnels simply because
regional media outlets haven't reported their existence. One would
actually expect to hear very little on the issue from traditional
news sources, because incursion tunnels are most useful when they
remain unknown to the enemy; otherwise, the opposing side would
carry out disruptive countermeasures, (e.g. the abovementioned
counter-tunnel-tunnels dug by the Viennese against the Ottoman Turks).
As such, it stands to reason that the Karabakh combatants wouldn't
inform their own national media about their covert/clandestine
underground activities. It's also quite possible that government or
military officials have explicitly instructed, or else pressured their
country's reporters to refrain from reporting on the issue, citing
national security concerns. This theory, however, fails to explain
why Azerbaijan doesn't publicize Armenia's tunnels and vice-versa. To
account for this reality, an observer would likely arrive at one
of the following conclusions: the sides simply aren't tunneling
(see Hypotheses 1 and 2); neither side knows if, or where the enemy
has engaged in tunneling operations; or lastly, the combatants are
keeping their knowledge of enemy digging operations secret, in order to
preserve the element of strategic surprise in a contingency situation,
i.e. depriving the enemy of an asset, which the latter had integrated
into its war plans. The latter two explanations, therefore, indicate
there are at least a few realistic scenarios in which unpublicized
tunneling might occur.
If Azerbaijan and Armenia are indeed engaged in underground tunneling,
one would naturally be interested in determining the nature and scale
of these operations. To accomplish this goal, it would be prudent to
refer to antecedent case studies in order to draw appropriate lessons
and rules of thumb. One North Korean incursion tunnel, for instance,
is reported to be a mile long, two meters across, and two meters high.
Reports also indicate it's large enough to allow 30,000 soldiers to
pass through every hour.[xviii],[xix] Given these dimensions, it's
clear the tunnel was designed with strategic objectives and missions
in mind, i.e. a full-blown invasion of the south. Tunnels of a more
tactical nature, however, will likely be smaller in scale and length.
Therefore, in drawing parallels to the Karabakh conflict, one should
first try to understand the antagonists' doctrine and end-goals,
as well as their manpower and resources.
With respect to the latter, Azerbaijan frequently demonstrates its
growing offensive capability by way of huge arms purchases, ballooning
defense budgets, and technological advances; the country also claims
its military is capable of liberating all disputed territory within
10 days.[xx]Azerbaijan's official, parliament-sanctioned doctrine
is also readily available on the internet, and it (not surprisingly)
establishes the country's right to use military force to "liberate"
Nagorno Karabakh.[xxi] Given this information, there is little reason
to doubt that Baku may have actual plans to eventually breach the
line of contact and invade Karabakh, even if its near term goal in
making these belligerent proclamations is merely to intimidate the
Armenian side into sacrificing additional concessions in the ongoing
Minsk Group negotiations. Whether these plans entail the conquest
of all of Karabakh or are of a more limited nature, however, is
a matter of a great deal of speculation.[xxii],[xxiii] Moreover,
one should also consider the fact that plans can quickly change or
become obsolete depending on circumstances on the ground, and in this
respect, Azerbaijan's objectives may shift as it succeeds or fails
to attain near-term objectives. Regardless, any major offensive would
likely require Azerbaijani forces to quickly penetrate multiple layers
of defense.
North Korean-style, strategic tunnels, therefore, should prove
appealing to Azerbaijan (Hypothesis 3), since they theoretically would
spare its forces from having to engage in high-casualty human wave
attacks. This latter point is of prime importance, since traditional
military theory asserts that the attacking side should have at least
a three to one numerical superiority over a defender in order to
have a reasonable chance of success.[xxiv] According to open source
reporting, Azerbaijan is presently assessed to have ~95K personnel
(plus reservists), while Armenia and Karabakh together are thought
have a cumulative of ~67K personnel (plus reservists).[xxv],[xxvi]
Consequently, Azerbaijan may only have a numerical superiority of
three to two, although local disparities and concentrations can vary
to some extent. Regardless, Baku would likely seek ways to bridge any
personnel shortages via force multipliers (e.g. superior equipment
or command & communication infrastructure), and force preservation
measures (e.g. incursion tunnels).
With respect to Armenian doctrine and capabilities, it is often assumed
that the country maintains an exclusively defensive posture, because
it already occupies most of the territory of the former Nagorno
Karabakh Autonomous Oblast - meaning, it's relatively satisfied
with the status quo. Nevertheless, senior Armenian military leaders
occasionally indicate that they too reserve the option of carrying out
an preemptive strike against Azerbaijan if the latter felt it necessary
to secure Karabakh.[xxvii],[xxviii] As with Azerbaijan, it's difficult
to determine if this rhetoric is simply propaganda or if it reflects
genuine policy per se, although Armenia's acquisition of short range
(300 km) surface-to-surface missiles suggests there is at least some
desire in Yerevan to develop strategic offensive capabilities.[xxix]
Therefore, it's not outside the realm of possibilities to assess
that Armenia may also seek and/or possesses strategic-scale incursion
tunnels bisecting the line-of-contact.
Whether they're Azerbaijani or Armenian, these hypothesized invasion
tunnels would most likely be located in areas that possess some
combination of the following attributes: 1) favorable geology and
topography; 2) adversary deemed to be particularly vulnerable; 3) a
lighting offensive would surprise the enemy. For instance, the geology
near Agdam may be conducive to tunnel digging (supporting factor 1),
but many analysts have speculated that an Azerbaijani offensive in
this area is among the most likely scenarios (partially undermining
factor 3).[xxx]Strategists in Baku, therefore, would have to weigh
these respective advantages and disadvantages accordingly. Planners
must also consider the risk that the enemy will discover the location
of their strategic tunnels, as this would result wasted resources as
well as ruined operational plans. This fear, in turn, would likely
preclude either side from using strategic tunnels for minor punitive
attacks. In other words, once built, these tunnels will most likely
remain unused.
Hypothesis 4
In contrast with strategic tunnels, combatants may tempted to actually
use smaller, tactical tunnels in the current environment, because
their discovery would not necessarily ruin any invasion-scenario
war plans. Such tunnels, in fact, could theoretically explain
how commandos sometimes succeed in sneaking across a no-mans-land,
which is ostensibly littered with minefields and sniper nests.[xxxi]
However, this theory appears to be partly undercut by reporting of
alleged civilians and conscripts inadvertently wondering across the
line-of-contact, suggesting the front is not entirely impervious to
overland excursions.[xxxii],[xxxiii],[xxxiv]
Another reason this hypothesis falls short is because regional
English-language media have not reported the existence of enemy
expendable/one-time-use tunnels, even though (as mentioned above), such
a disclosure would not affect either side's war plans (in contrast
with strategic tunnels). Indeed, there is no obvious reason for
Azerbaijani or Armenian officials to withhold from their respective
media outlets the fact that such tunnels were discovered in post
commando-raid investigations. Advocates of the fourth hypothesis may
also postulate that the combatants are simply unable to locate enemy
tunnels - even after they've been used in a putative attack.
This explanation, however, seems fairly implausible, given the
forensic/investigative technology likely in possession of both sides;
but this author concedes that there may be a few situations where
post-use tunnels remain undetected (e.g. extremely complex terrain).
In any event, the fourth hypothesis appears less likely than the third.
Locating Hidden Tunnels
While any of the above mentioned hypotheses is possible, it would
be wise for the warring sides to anticipate a worst case scenario,
which in this case, stipulates that one or both combatants have
constructed secret, strategic tunnels to be used in a future,
large-scale offensive (hypothesis 3). With this threat in mind,
one might ask what the Armenian side is doing in order to detect
dormant Azerbaijani incursion tunnels - and vice-versa. To answer
these rhetorical questions, one should first consider past precedent.
As mentioned earlier, U.S. border patrol officers routinely locate
narcotics tunnels that bisect the Mexican border. According to open
source reporting, many of these were discovered through the use of
informants, or else were chanced upon by officers out on patrol.[xxxv]
Similarly, one of the aforementioned Korean incursion tunnels was
supposedly disclosed via a North Korean defector, and another was
located after South Korean soldiers observed steam suspiciously
emanating from the ground.[xxxvi],[xxxvii] Given the above, it
appears human intelligence (HUMINT) is a fairly effective method for
discovering clandestine underground activity. This is especially
applicable in the Karabakh conflict, considering recent reports,
which indicate that Armenian and Azerbaijani intelligence services
regularly task recruited sources with collecting intelligence on the
military activities and capabilities of the enemy.[xxxviii],[xxxix]
Thus, one should expect sources to be specifically charged with
determining the existence and location of tunnels along the front.
Although HUMINT may be a time tested collection method, the two
Karabakh combatants may also be relying upon more modern, high-tech
means to detect nefarious underground activity. Among the more
interesting methods is acoustic seismology, which essentially entails
sending compression/acoustic waves through the ground and recording
the subsequent reverberations. Based on the varying densities
of underground material, different (i.e. time delayed) acoustic
reflections will be recorded by a sensor on the surface. One should,
therefore, be able to detect a tunnel, since the air that occupies it
is significantly less dense than the surrounding rock.[xl]The United
States itself has explored the possibility of using this method
to find narcotics tunnels, but technological challenges remain an
impediment (e.g. those pertaining to irregular tunnel shape).[xli]
Thus, one could speculate that Azerbaijan or Armenia likely find
acoustic seismology equally unreliable.
As far as high-tech gadgetry is concerned, a more appealing option
may be ground penetrating radar. Indeed, a number of manufacturers
specifically tout their systems' military applications, including
their ability to detect concealed tunnels.[xlii] As one may infer,
this method relies on electromagnetic (vice acoustic, transmissions)
and could theoretically allow one to detect underground anomalies
up to 50 feet deep. Ground penetrating radar, nevertheless, has its
own limitations, including degraded performance when operating over
ground that is heterogeneous in composition.[xliii] Therefore, if
the soil near the Karabakh line-of-contact is too stony, this method
could prove ineffective.
While there may be countless additional ways for Armenia or
Azerbaijan to locate hidden tunnels, for the sake of brevity this
paper will focus on just one more - namely, cutting edge infrared
cameras. As mentioned earlier, South Korean soldiers were able to
find an incursion tunnel after observing a suspicious steam vent
during a late-November patrol in the 1970s.[xliv]Operating on the
same concept, modern infrared cameras are capable of detecting minute
temperature changes that occur as a result of underground tunneling
operations. In fact, this method has already been field-tested along
the U.S. border with varying success, and a number of private firms
claim they are able to detect hidden tunnels by conducting infrared
pattern analysis, i.e. comparing before-and-after infrared images of
the same area.[xlv],[xlvi]Nevertheless, the technique still appears
to be in the developmental stage, which may dissuade the Karabakh
factions from following suit.
Conclusion
Considering the above analysis, what are the implications for
the Karabakh conflict? Given their historical use and potential
effectiveness, it's possible both sides are furiously digging
tunnels in preparation for a major invasion or preemptive attack. By
extrapolating from the Korea precedent, these theorized tunnels have
the potential to significantly alter the course of events should a
major war re-erupt. Tens of thousands of troops could simply bypass
heavily fortified trenches - thereby sparing them from mass casualties,
while also allowing them to wreak havoc in the enemy's rear areas. In
essence, tunnels could be a game changer.
Conversely, there's a decent chance that the above fear is sheer
speculation and that Azerbaijan and Armenia are not engaged any
underground excavation whatsoever. Either way, the public is in
the dark (no pun intended), since the absence of evidence does not
necessarily signify evidence of absence. Moreover, since military
leaders from both sides are faced with a similar conundrum, it would be
logical for them to dig tunnels, because they would (or should) assume
that their foes are doing the exact same thing. Operating according
to this prisoner's dilemma-type logic ensures that neither side
relinquishes some theorized strategic advantage. Prudent commanders
will also likely try to shed light on the matter by seeking to confirm
or deny the existence enemy tunnels by using some or all of the means
discussed in the section directly above. Thus, a lot may be going on
along the Karabakh line-of-contact, which hasn't yet come to light
(pun intended).
[i]
http://armenianow.com/karabakh/55432/armenia_karabakh_soldiers_killed
[ii]
http://news.bbc.co.uk/2/hi/programmes/this_world/one_day_of_war/3622431.stm
[iii]
http://www.opendemocracy.net/od-russia/thomas-de-waal/nagorno-karabakh-crimea-doppelganger-azerbaijan-armenia
[iv] http://mondediplo.com/2012/12/12karabakh
[v] http://news.am/eng/news/201998.html
[vi]http://armenianow.com/karabakh/54744/armenia_karabakh_azerbaijan_ceasefire_violation_in flitration_attempt
[vii] http://www.freerepublic.com/focus/news/2424922/posts
[viii]
http://www.channel5.com/shows/ww1s-tunnels-of-death-the-big-dig/episodes/earthquaking-the-ridge
[ix]
http://en.wikipedia.org/wiki/North_Korean_infiltration_tunnels#Incursion_tunnel s
[x]
http://fortunascorner.com/2013/04/22/north-korea-may-have-13-undiscovered-invasion-tunnels/
[xi] http://www.cnn.com/2013/10/31/us/mexico-drug-tunnel/index.html
[xii] http://www.cnn.com/2010/CRIME/11/03/san.diego.border.tunnel/
[xiii]
http://uk.reuters.com/article/2012/09/11/uk-azerbaijan-armenia-conflict-military-idUKBRE88A0F720120911
[xiv]
http://www.usatoday.com/story/news/world/2014/01/14/drug-tunnels-us-mexico-border/4478073/
[xv] http://en.wikipedia.org/wiki/Battle_of_Kelbajar
[xvi]
http://4.bp.blogspot.com/-Phs_pAuJtv0/UGw7AvET8hI/AAAAAAAABPs/Oa4ofXf_1KU/s1600/16.jpg
[xvii] http://hetq.am/eng/multimedia/slideshows/59
[xviii] http://en.wikipedia.org/wiki/Third_Tunnel_of_Aggression
[xix]http://blogs.telegraph.co.uk/news/malcolmmoore/9902611/Inside_North_Koreas_Third_Tunnel_of_Aggression/
[xx]
http://hetq.am/eng/news/15312/azerbaijani-press-review-azerbaijani-army-needs-10-days-to-liberate-occupied-lands.html
[xxi]
http://biweekly.ada.edu.az/vol_3_no_12/Newly_approved_military_doctrine_Goble.htm
[xxii]
http://asbarez.com/78940/assessing-azerbaijan%E2%80%99s-military-threat-to-retake-karabakh/
[xxiii]
http://www.armenianweekly.com/2014/01/05/artsakhs-prospects-for-the-future/
[xxiv] http://smallwarsjournal.com/blog/journal/docs-temp/647-thiel.pdf
[xxv] http://www.globalsecurity.org/military/world/azerbaijan/intro.htm
[xxvi] http://en.wikipedia.org/wiki/Armenian_military
[xxvii] http://www.azatutyun.am/content/article/24981715.html
[xxviii]
http://www.armenianow.com/news/9132/offense_taken_aliyev_talks_tough_i
[xxix] http://www.azatutyun.am/content/article/24335604.html
[xxx]
http://www.armenianweekly.com/2014/01/05/artsakhs-prospects-for-the-future/
[xxxi]
http://www.rferl.org/content/azerbaijan-karabakh-soldier-killed/25235874.html
[xxxii]
http://asbarez.com/120184/armenian-villager-captured-by-azeris-returns-home/
[xxxiii]
http://www.armradio.am/en/2014/03/08/another-armenian-villager-captured-by-azeris/
[xxxiv] http://news.am/eng/news/114859.html
[xxxv]
http://www.usatoday.com/story/news/world/2014/01/14/drug-tunnels-us-mexico-border/4478073/
[xxxvi] http://en.wikipedia.org/wiki/Third_Tunnel_of_Aggression
[xxxvii]
http://en.wikipedia.org/wiki/Korean_Demilitarized_Zone#Incursion_tunnels
[xxxviii] http://www.lragir.am/index/eng/0/right/wv5k/31865
[xxxix]
http://asbarez.com/72188/armenia-arrests-two-on-charges-of-spying-for-azerbaijan/
[xl] http://en.wikipedia.org/wiki/Reflection_seismology
[xli] http://ncpa.olemiss.edu/seismic-tunnel-detection/
[xlii] http://www.geophysical.com/militarysecurity.htm
[xliii] http://en.wikipedia.org/wiki/Ground-penetrating_radar
[xliv] http://en.wikipedia.org/wiki/Korean_DMZ#Incursion_tunnels
[xlv]
http://www.entechworld.com/services/subterranean_tunnel_detection#tab-1
[xlvi]
http://www.insightcrime.org/news-analysis/tunnel-detection-technology-at-mexico-border-worth-the-effort
Posted on August 13, 2014 Karabakh
https://karabakhsecurityanalysis.wordpress.com/2014/08/13/underground-intrigue-a-conjectural-assessment-of-incursion-tunnels-in-a-future-nagorno-karabakh-conflict/
Overview and Background
2014 already appears to be as bloody, if not more so, than previous
years along the front lines of the Nagorno Karabakh conflict. It
seems that every week or two the so-called frozen conflict claims a
new victim - typically a young Armenian or Azerbaijani soldier, but
on occasion an innocent civilian who ended up in the wrong place at
the wrong time. While the majority of the fatal ceasefire violations
occur along the de facto Nagorno Karabakh Republic - Azerbaijani line
of contact, they have also broken out along Armenia's northeastern
international border with Azerbaijan. More worrisome still, recent
reports suggest that the violence may also be spreading to Armenia's
southwestern border with Azerbaijan's Nakhchivan exclave.[i]
A plethora of documentaries and articles have sought to capture the
tense atmosphere at the front - with commentators often comparing the
situation to the type of trench warfare that occurred on the Western
Front during World War I.[ii],[iii],[iv] Similar to Verdun, France one
hundred years ago, two entrenched and generally static forces face off
against each other along the Karabakh line of contact. Corroborated by
a casual Google Earth investigation, reports suggest opposing trenches
are, at places, separated by only a few dozen yards. Recent fatalities
also indicate minefields are scattered throughout no-man's-land,
although it's not entirely clear whether these are newly emplaced or
remnants from the hot war that ended in 1994.[v] There are a number
of acute differences between the Karabakh situation and prototypical
trench warfare, however. Perhaps the most obvious is the fact that
the Karabakh conflict no longer includes human wave attacks, although
these suicidal charges did occur in the waning days of the war.
While major offensives no longer seem to be in the offing, at least
in the near term, regional news reports reveal that 'commando raids'
still occur on a frequent basis.[vi] It's difficult to ascertain which
side is responsible for the raids owing to mutual recriminations, but
on the face of it, Azerbaijan seems to have the most to gain from such
provocations considering it's the least satisfied with the status quo.
Nevertheless, it's reasonable to assume the Armenian side also stages
punitive attacks to demonstrate its resolve and military capability.
The situation along the line of contact, therefore, can best be
described as unstable, but with neither side willing to commit to a
major offensive designed to capture territory. However, the purpose
of this article is not to recap the current situation on the ground,
but to focus on another aspect of the Karabakh conflict that doesn't
receive coverage - namely, what's going on underground. In other
words, this paper will explore the use, or non-use, of offensive
incursion tunnels.
Armies have employed tunneling to bypass or undermine fixed defenses
for hundreds if not thousands of years. The Ottoman Turks employed the
technique in an attempt to capture Vienna in the 16th century only
to be thwarted by the city's defenders, who successfully dug what
can best be described as counter-tunnels.[vii] During World War I,
opposing armies hoped tunnels could help break the trench-warfare
stalemate.[viii] Moreover, one should not mistake this tactic to be
some obsolete historical relic, as four North Korean incursion tunnels,
large enough to accommodate an invasion force of thousands, were
discovered in the latter half of the 20th century; and commentators
speculate that there may be dozens more yet to be discovered.[ix],[x]
Even in our back yard, Mexican drug cartels successfully dig secret
tunnels to bypass the heavily fortified and monitored southern
U.S. border.[xi],[xii]
Given the evident utility of tunneling, it's reasonable to ask why
Azerbaijanis or Armenians aren't employing the method to circumvent
or bypass the heavily defended Karabakh line of contact. A more
circumspect individual might caveat the question by further asking
why neither side has reported the use of tunneling, since a fairly
comprehensive, English-language, internet search yields almost no
substantive documentation on the subject - hypothetical or factual
(there admittedly are a few passing references in forums). After
ruminating over the mystery a while, one would likely arrive at one
or several of the following explanations:
(Hypothesis 1) Neither side is able to dig incursion tunnels for
financial or technical reasons.
(Hypothesis 2) The opposing forces deliberately choose not to dig
tunnels despite the fact that they are physically capable of doing so.
(Hypothesis 3) The sides have indeed built secret contingency/incursion
tunnels, which will only be used if/when the conflict reverts to
a hot-war.
(Hypothesis 4) Armenian and Azerbaijani forces actually use tunnels
on a regular basis to stage commando raids, but choose not to release
this information to the press.
Hypothesis 1
In evaluating these four options, it seems the first scenario can be
safely discarded for a number of reasons. Azerbaijan frequently boasts
that its annual defense budget is larger than Armenia's entire state
budget, because of its burgeoning oil industry. This fact alone
indicates the country is financially capable of digging tunnels
only a few hundred yards in length, especially considering precious
instances where less-endowed antagonists were able to afford similar
undertakings, e.g. North Korea. While the Armenian/Karabakh side is
admittedly poorer than its rival, Armenia's annual defense budget
is still ~400 million dollars per year. This figure is more than a
hundred times the amount purportedly needed to build a sophisticated
narcotics tunnel beneath the Mexican-US border.[xiii],[xiv] In other
words, Armenia would only need to devote one or two percent of its
military budget to carry out this type of activity, which is hardly
an insufferable expense.
Technical challenges also fail to satisfactorily explain the apparent
lack underground excavation. While the topography of the line of
contact is indeed rugged and daunting at places, it nevertheless
remains surmountable from an engineering standpoint. An anecdotal
example that reflects this reality is the strategic auto-tunnel that
lies the south of Kelbajar.[xv] From a more macro-scale geological
perspective, much of the line of contact is situated on ground
that is composed of flood plain, alluvial deposits.[xvi] This loose
soil/gravel/stony mixture usually doesn't require dynamite or heavy
equipment to move, which seems evident enough after viewing photos of
existing trenches on the frontline.[xvii] There is one noteworthy
exception to this general rule, however; namely, the east-west
running Murovdag/Mrav mountain range, which consists of harder basalt,
sandstone and limestone. In any case, if the opposing sides wanted
to engage in tunneling, it appears they would be able to do so -
at least for most sections of the front.
Hypothesis 2
The second explanatory hypothesis considers the possibility that
there is a de facto - if not de jure - policy against underground
excavation. There are a number of reasons why a leader might
deliberately choose to forgo the advantages derived from tunneling.
For instance, they may fear a scenario in which the adversary showcases
a discovered tunnel to prove that the other is acting in bad faith
vis-a-vis the ceasefire regime. This theory breaks down under closer
scrutiny, however, because the antagonists, Azerbaijan in particular,
do not appear to be overly fearful of making truculent statements
and carrying out provocative actions. This is best exemplified by
Baku's 2012 decision to free and publically venerate Ramil Safarov,
who brutally murdered an Armenian serviceman during a NATO exercise in
Hungary. This inflammatory action generated nearly universal western
condemnation, yet Azerbaijan adamantly maintains that it was acting
well within its rights. In a similar vein, Baku frequently claims it is
developing and/or possesses the military capability to forcibly resolve
the Karabakh conflict in the event that the ongoing Minsk Group break
down, which could antagonize European and American interlocutors who
repeatedly proclaim that there is no military solution to the Karabakh
issue. Given this behavior, it seems unlikely that Azerbaijan would
shun subterranean activity solely to avoid hypothetical Western
criticism. And even if Armenian forces were to claim that they
located an Azerbaijani incursion tunnel, Baku could always deny any
responsibly or else could call such accusations "lies," which would
serve to ensure that true and accurate revelations get lost in the
broader propaganda war currently being waged between the two countries.
Another factor that may deter political or military commanders from
ordering underground operations is the prospect that such a decision
could needlessly and dangerously destabilize the line of contact,
and, by extension, the status quo. While the current situation on
the front is bloody, it is nevertheless predictable, if not well
managed. After one or two soldiers are killed on one side, several
troops on the opposing side will typically end up getting shot over
the course of the next several days; this cycle then repeats itself on
a periodic basis. Introducing tunneling into the equation, however,
could jeopardize this set pattern by allowing one or both sides to
engage in asymmetrical retaliation. Provided the antagonists are able
to covertly enter enemy territory via incursion tunnels, one side could
swiftly kill a dozen rivals to avenge the death of one of their own.
This in turn may precipitate an escalating response from the enemy
(e.g. heavy artillery), which would set in motion an unexpected and
undesired chain of events that could easily spiral out of control.
Thus, since neither side is interested in an accidental war, it's
possible they have arrived at some sort of de facto or gentlemen's
agreement to avoid underground warfare altogether.
Hypothesis 3
While the preceding theories explain why incursion tunnels haven't
been constructed along the line of contact, it's entirely conceivable
that we (the public) are unaware of existing tunnels simply because
regional media outlets haven't reported their existence. One would
actually expect to hear very little on the issue from traditional
news sources, because incursion tunnels are most useful when they
remain unknown to the enemy; otherwise, the opposing side would
carry out disruptive countermeasures, (e.g. the abovementioned
counter-tunnel-tunnels dug by the Viennese against the Ottoman Turks).
As such, it stands to reason that the Karabakh combatants wouldn't
inform their own national media about their covert/clandestine
underground activities. It's also quite possible that government or
military officials have explicitly instructed, or else pressured their
country's reporters to refrain from reporting on the issue, citing
national security concerns. This theory, however, fails to explain
why Azerbaijan doesn't publicize Armenia's tunnels and vice-versa. To
account for this reality, an observer would likely arrive at one
of the following conclusions: the sides simply aren't tunneling
(see Hypotheses 1 and 2); neither side knows if, or where the enemy
has engaged in tunneling operations; or lastly, the combatants are
keeping their knowledge of enemy digging operations secret, in order to
preserve the element of strategic surprise in a contingency situation,
i.e. depriving the enemy of an asset, which the latter had integrated
into its war plans. The latter two explanations, therefore, indicate
there are at least a few realistic scenarios in which unpublicized
tunneling might occur.
If Azerbaijan and Armenia are indeed engaged in underground tunneling,
one would naturally be interested in determining the nature and scale
of these operations. To accomplish this goal, it would be prudent to
refer to antecedent case studies in order to draw appropriate lessons
and rules of thumb. One North Korean incursion tunnel, for instance,
is reported to be a mile long, two meters across, and two meters high.
Reports also indicate it's large enough to allow 30,000 soldiers to
pass through every hour.[xviii],[xix] Given these dimensions, it's
clear the tunnel was designed with strategic objectives and missions
in mind, i.e. a full-blown invasion of the south. Tunnels of a more
tactical nature, however, will likely be smaller in scale and length.
Therefore, in drawing parallels to the Karabakh conflict, one should
first try to understand the antagonists' doctrine and end-goals,
as well as their manpower and resources.
With respect to the latter, Azerbaijan frequently demonstrates its
growing offensive capability by way of huge arms purchases, ballooning
defense budgets, and technological advances; the country also claims
its military is capable of liberating all disputed territory within
10 days.[xx]Azerbaijan's official, parliament-sanctioned doctrine
is also readily available on the internet, and it (not surprisingly)
establishes the country's right to use military force to "liberate"
Nagorno Karabakh.[xxi] Given this information, there is little reason
to doubt that Baku may have actual plans to eventually breach the
line of contact and invade Karabakh, even if its near term goal in
making these belligerent proclamations is merely to intimidate the
Armenian side into sacrificing additional concessions in the ongoing
Minsk Group negotiations. Whether these plans entail the conquest
of all of Karabakh or are of a more limited nature, however, is
a matter of a great deal of speculation.[xxii],[xxiii] Moreover,
one should also consider the fact that plans can quickly change or
become obsolete depending on circumstances on the ground, and in this
respect, Azerbaijan's objectives may shift as it succeeds or fails
to attain near-term objectives. Regardless, any major offensive would
likely require Azerbaijani forces to quickly penetrate multiple layers
of defense.
North Korean-style, strategic tunnels, therefore, should prove
appealing to Azerbaijan (Hypothesis 3), since they theoretically would
spare its forces from having to engage in high-casualty human wave
attacks. This latter point is of prime importance, since traditional
military theory asserts that the attacking side should have at least
a three to one numerical superiority over a defender in order to
have a reasonable chance of success.[xxiv] According to open source
reporting, Azerbaijan is presently assessed to have ~95K personnel
(plus reservists), while Armenia and Karabakh together are thought
have a cumulative of ~67K personnel (plus reservists).[xxv],[xxvi]
Consequently, Azerbaijan may only have a numerical superiority of
three to two, although local disparities and concentrations can vary
to some extent. Regardless, Baku would likely seek ways to bridge any
personnel shortages via force multipliers (e.g. superior equipment
or command & communication infrastructure), and force preservation
measures (e.g. incursion tunnels).
With respect to Armenian doctrine and capabilities, it is often assumed
that the country maintains an exclusively defensive posture, because
it already occupies most of the territory of the former Nagorno
Karabakh Autonomous Oblast - meaning, it's relatively satisfied
with the status quo. Nevertheless, senior Armenian military leaders
occasionally indicate that they too reserve the option of carrying out
an preemptive strike against Azerbaijan if the latter felt it necessary
to secure Karabakh.[xxvii],[xxviii] As with Azerbaijan, it's difficult
to determine if this rhetoric is simply propaganda or if it reflects
genuine policy per se, although Armenia's acquisition of short range
(300 km) surface-to-surface missiles suggests there is at least some
desire in Yerevan to develop strategic offensive capabilities.[xxix]
Therefore, it's not outside the realm of possibilities to assess
that Armenia may also seek and/or possesses strategic-scale incursion
tunnels bisecting the line-of-contact.
Whether they're Azerbaijani or Armenian, these hypothesized invasion
tunnels would most likely be located in areas that possess some
combination of the following attributes: 1) favorable geology and
topography; 2) adversary deemed to be particularly vulnerable; 3) a
lighting offensive would surprise the enemy. For instance, the geology
near Agdam may be conducive to tunnel digging (supporting factor 1),
but many analysts have speculated that an Azerbaijani offensive in
this area is among the most likely scenarios (partially undermining
factor 3).[xxx]Strategists in Baku, therefore, would have to weigh
these respective advantages and disadvantages accordingly. Planners
must also consider the risk that the enemy will discover the location
of their strategic tunnels, as this would result wasted resources as
well as ruined operational plans. This fear, in turn, would likely
preclude either side from using strategic tunnels for minor punitive
attacks. In other words, once built, these tunnels will most likely
remain unused.
Hypothesis 4
In contrast with strategic tunnels, combatants may tempted to actually
use smaller, tactical tunnels in the current environment, because
their discovery would not necessarily ruin any invasion-scenario
war plans. Such tunnels, in fact, could theoretically explain
how commandos sometimes succeed in sneaking across a no-mans-land,
which is ostensibly littered with minefields and sniper nests.[xxxi]
However, this theory appears to be partly undercut by reporting of
alleged civilians and conscripts inadvertently wondering across the
line-of-contact, suggesting the front is not entirely impervious to
overland excursions.[xxxii],[xxxiii],[xxxiv]
Another reason this hypothesis falls short is because regional
English-language media have not reported the existence of enemy
expendable/one-time-use tunnels, even though (as mentioned above), such
a disclosure would not affect either side's war plans (in contrast
with strategic tunnels). Indeed, there is no obvious reason for
Azerbaijani or Armenian officials to withhold from their respective
media outlets the fact that such tunnels were discovered in post
commando-raid investigations. Advocates of the fourth hypothesis may
also postulate that the combatants are simply unable to locate enemy
tunnels - even after they've been used in a putative attack.
This explanation, however, seems fairly implausible, given the
forensic/investigative technology likely in possession of both sides;
but this author concedes that there may be a few situations where
post-use tunnels remain undetected (e.g. extremely complex terrain).
In any event, the fourth hypothesis appears less likely than the third.
Locating Hidden Tunnels
While any of the above mentioned hypotheses is possible, it would
be wise for the warring sides to anticipate a worst case scenario,
which in this case, stipulates that one or both combatants have
constructed secret, strategic tunnels to be used in a future,
large-scale offensive (hypothesis 3). With this threat in mind,
one might ask what the Armenian side is doing in order to detect
dormant Azerbaijani incursion tunnels - and vice-versa. To answer
these rhetorical questions, one should first consider past precedent.
As mentioned earlier, U.S. border patrol officers routinely locate
narcotics tunnels that bisect the Mexican border. According to open
source reporting, many of these were discovered through the use of
informants, or else were chanced upon by officers out on patrol.[xxxv]
Similarly, one of the aforementioned Korean incursion tunnels was
supposedly disclosed via a North Korean defector, and another was
located after South Korean soldiers observed steam suspiciously
emanating from the ground.[xxxvi],[xxxvii] Given the above, it
appears human intelligence (HUMINT) is a fairly effective method for
discovering clandestine underground activity. This is especially
applicable in the Karabakh conflict, considering recent reports,
which indicate that Armenian and Azerbaijani intelligence services
regularly task recruited sources with collecting intelligence on the
military activities and capabilities of the enemy.[xxxviii],[xxxix]
Thus, one should expect sources to be specifically charged with
determining the existence and location of tunnels along the front.
Although HUMINT may be a time tested collection method, the two
Karabakh combatants may also be relying upon more modern, high-tech
means to detect nefarious underground activity. Among the more
interesting methods is acoustic seismology, which essentially entails
sending compression/acoustic waves through the ground and recording
the subsequent reverberations. Based on the varying densities
of underground material, different (i.e. time delayed) acoustic
reflections will be recorded by a sensor on the surface. One should,
therefore, be able to detect a tunnel, since the air that occupies it
is significantly less dense than the surrounding rock.[xl]The United
States itself has explored the possibility of using this method
to find narcotics tunnels, but technological challenges remain an
impediment (e.g. those pertaining to irregular tunnel shape).[xli]
Thus, one could speculate that Azerbaijan or Armenia likely find
acoustic seismology equally unreliable.
As far as high-tech gadgetry is concerned, a more appealing option
may be ground penetrating radar. Indeed, a number of manufacturers
specifically tout their systems' military applications, including
their ability to detect concealed tunnels.[xlii] As one may infer,
this method relies on electromagnetic (vice acoustic, transmissions)
and could theoretically allow one to detect underground anomalies
up to 50 feet deep. Ground penetrating radar, nevertheless, has its
own limitations, including degraded performance when operating over
ground that is heterogeneous in composition.[xliii] Therefore, if
the soil near the Karabakh line-of-contact is too stony, this method
could prove ineffective.
While there may be countless additional ways for Armenia or
Azerbaijan to locate hidden tunnels, for the sake of brevity this
paper will focus on just one more - namely, cutting edge infrared
cameras. As mentioned earlier, South Korean soldiers were able to
find an incursion tunnel after observing a suspicious steam vent
during a late-November patrol in the 1970s.[xliv]Operating on the
same concept, modern infrared cameras are capable of detecting minute
temperature changes that occur as a result of underground tunneling
operations. In fact, this method has already been field-tested along
the U.S. border with varying success, and a number of private firms
claim they are able to detect hidden tunnels by conducting infrared
pattern analysis, i.e. comparing before-and-after infrared images of
the same area.[xlv],[xlvi]Nevertheless, the technique still appears
to be in the developmental stage, which may dissuade the Karabakh
factions from following suit.
Conclusion
Considering the above analysis, what are the implications for
the Karabakh conflict? Given their historical use and potential
effectiveness, it's possible both sides are furiously digging
tunnels in preparation for a major invasion or preemptive attack. By
extrapolating from the Korea precedent, these theorized tunnels have
the potential to significantly alter the course of events should a
major war re-erupt. Tens of thousands of troops could simply bypass
heavily fortified trenches - thereby sparing them from mass casualties,
while also allowing them to wreak havoc in the enemy's rear areas. In
essence, tunnels could be a game changer.
Conversely, there's a decent chance that the above fear is sheer
speculation and that Azerbaijan and Armenia are not engaged any
underground excavation whatsoever. Either way, the public is in
the dark (no pun intended), since the absence of evidence does not
necessarily signify evidence of absence. Moreover, since military
leaders from both sides are faced with a similar conundrum, it would be
logical for them to dig tunnels, because they would (or should) assume
that their foes are doing the exact same thing. Operating according
to this prisoner's dilemma-type logic ensures that neither side
relinquishes some theorized strategic advantage. Prudent commanders
will also likely try to shed light on the matter by seeking to confirm
or deny the existence enemy tunnels by using some or all of the means
discussed in the section directly above. Thus, a lot may be going on
along the Karabakh line-of-contact, which hasn't yet come to light
(pun intended).
[i]
http://armenianow.com/karabakh/55432/armenia_karabakh_soldiers_killed
[ii]
http://news.bbc.co.uk/2/hi/programmes/this_world/one_day_of_war/3622431.stm
[iii]
http://www.opendemocracy.net/od-russia/thomas-de-waal/nagorno-karabakh-crimea-doppelganger-azerbaijan-armenia
[iv] http://mondediplo.com/2012/12/12karabakh
[v] http://news.am/eng/news/201998.html
[vi]http://armenianow.com/karabakh/54744/armenia_karabakh_azerbaijan_ceasefire_violation_in flitration_attempt
[vii] http://www.freerepublic.com/focus/news/2424922/posts
[viii]
http://www.channel5.com/shows/ww1s-tunnels-of-death-the-big-dig/episodes/earthquaking-the-ridge
[ix]
http://en.wikipedia.org/wiki/North_Korean_infiltration_tunnels#Incursion_tunnel s
[x]
http://fortunascorner.com/2013/04/22/north-korea-may-have-13-undiscovered-invasion-tunnels/
[xi] http://www.cnn.com/2013/10/31/us/mexico-drug-tunnel/index.html
[xii] http://www.cnn.com/2010/CRIME/11/03/san.diego.border.tunnel/
[xiii]
http://uk.reuters.com/article/2012/09/11/uk-azerbaijan-armenia-conflict-military-idUKBRE88A0F720120911
[xiv]
http://www.usatoday.com/story/news/world/2014/01/14/drug-tunnels-us-mexico-border/4478073/
[xv] http://en.wikipedia.org/wiki/Battle_of_Kelbajar
[xvi]
http://4.bp.blogspot.com/-Phs_pAuJtv0/UGw7AvET8hI/AAAAAAAABPs/Oa4ofXf_1KU/s1600/16.jpg
[xvii] http://hetq.am/eng/multimedia/slideshows/59
[xviii] http://en.wikipedia.org/wiki/Third_Tunnel_of_Aggression
[xix]http://blogs.telegraph.co.uk/news/malcolmmoore/9902611/Inside_North_Koreas_Third_Tunnel_of_Aggression/
[xx]
http://hetq.am/eng/news/15312/azerbaijani-press-review-azerbaijani-army-needs-10-days-to-liberate-occupied-lands.html
[xxi]
http://biweekly.ada.edu.az/vol_3_no_12/Newly_approved_military_doctrine_Goble.htm
[xxii]
http://asbarez.com/78940/assessing-azerbaijan%E2%80%99s-military-threat-to-retake-karabakh/
[xxiii]
http://www.armenianweekly.com/2014/01/05/artsakhs-prospects-for-the-future/
[xxiv] http://smallwarsjournal.com/blog/journal/docs-temp/647-thiel.pdf
[xxv] http://www.globalsecurity.org/military/world/azerbaijan/intro.htm
[xxvi] http://en.wikipedia.org/wiki/Armenian_military
[xxvii] http://www.azatutyun.am/content/article/24981715.html
[xxviii]
http://www.armenianow.com/news/9132/offense_taken_aliyev_talks_tough_i
[xxix] http://www.azatutyun.am/content/article/24335604.html
[xxx]
http://www.armenianweekly.com/2014/01/05/artsakhs-prospects-for-the-future/
[xxxi]
http://www.rferl.org/content/azerbaijan-karabakh-soldier-killed/25235874.html
[xxxii]
http://asbarez.com/120184/armenian-villager-captured-by-azeris-returns-home/
[xxxiii]
http://www.armradio.am/en/2014/03/08/another-armenian-villager-captured-by-azeris/
[xxxiv] http://news.am/eng/news/114859.html
[xxxv]
http://www.usatoday.com/story/news/world/2014/01/14/drug-tunnels-us-mexico-border/4478073/
[xxxvi] http://en.wikipedia.org/wiki/Third_Tunnel_of_Aggression
[xxxvii]
http://en.wikipedia.org/wiki/Korean_Demilitarized_Zone#Incursion_tunnels
[xxxviii] http://www.lragir.am/index/eng/0/right/wv5k/31865
[xxxix]
http://asbarez.com/72188/armenia-arrests-two-on-charges-of-spying-for-azerbaijan/
[xl] http://en.wikipedia.org/wiki/Reflection_seismology
[xli] http://ncpa.olemiss.edu/seismic-tunnel-detection/
[xlii] http://www.geophysical.com/militarysecurity.htm
[xliii] http://en.wikipedia.org/wiki/Ground-penetrating_radar
[xliv] http://en.wikipedia.org/wiki/Korean_DMZ#Incursion_tunnels
[xlv]
http://www.entechworld.com/services/subterranean_tunnel_detection#tab-1
[xlvi]
http://www.insightcrime.org/news-analysis/tunnel-detection-technology-at-mexico-border-worth-the-effort