A Review Of The Use Of Tunnels By Hamas, Hizbullah, Al-Qaeda, ISIS, Ansar Allah (Houthis), And Other Jihadi Groups And Ramifications For U.S. National Security – With Foreword By General (Ret) Kenneth F. McKenzie Jr., USMC

Table of Contents

FOREWORD BY GENERAL (RET) KENNETH F. MCKENZIE JR., USMC

Introduction

• The U.S. Military And The Defense Advanced Research Projects Agency (DARPA): Cutting-Edge Tunnel Research

• Under The U.S.-Mexico Border, Smugglers Have Used Hundreds Of Tunnels Over Two Decades – And ISIS Supporters Have Noticed

• A Look At Canada-U.S. Tunnels

Islamic State (ISIS) Used Tunnels In Iraq, Syria, And Afghanistan; Publications Instruct On And Encourage Tunnel Construction

• ISIS Supporter Shares Tunnel-Building Manual Based On Work Of ISIS Supporter In Gaza

• ISIS Tunnels Discovered In Iraq

• ISIS Tunnels Discovered In Syria And Afghanistan

• ISIS Publications Encouraging And Instructing On Digging Tunnels

Hurras Al-Din, The Al-Qaeda Affiliate In Syria, Digging Trenches, Fortifications

Hay'at Tahrir Al-Sham (HTS) Uses Tunnels For Defense Against Airstrikes, As "Terrifying Examples For The Enemies," And A "Popular Culture"

• HTS Halts Syrian Military Through Use Of Defensive And Offensive "Explosive Tunnels"

• HTS: Gaza Owes Its "Legendary Steadfastness" To Tunnels

• HTS Construction And Use Of Tunnels

• HTS Construction And Use Of Trenches

• HTS Construction And Use Of Fortifications

Hizbullah, Its Tunnels, And The October 7 Massacre In Israel

• Hizbullah Statements And Publications Featuring Tunnels

• Hizbullah Digs Tunnels Under Lebanon-Israel Border In Violation Of UNSC Resolution 1701

• Some Hizbullah Tunnels Dug Before 2006

• Lebanese Daily: Hizbullah Has Stationed Its Elite Unit In Shab'a Farms Area In South Lebanon, On High Alert And With Special Gear

• "Hizbullah Had Trained Hamas" To Dig Tunnels

• Israel's Invasion Of Southern Lebanon Reveals Hizbullah's Vast Tunnel Network, Stockpiles Of Weapons, And Military Plans – October 2024

Yemen's Ansar Allah Houthi Movement Train Using Tunnels

"The Gaza Metro" – Hamas's October 7 Attack And Its Tunnels In The Gaza Strip

• Confronted By The Hamas Tunnel Network In Gaza City And Rafah, The Israeli Military Has Adjusted Upward Its Estimate Of Its Size Since October 7

• Hamas Tunnels In The West Bank

• A Historical Look At Egypt's Tunnels To Gaza And The Muslim Brotherhood's Support In Developing Them

• Report On Hamas' Tunnel Complex In Gaza: Tunnels Suffered Only Limited Damage, Are Operational And Constitute A Strategic Weapon For Future War With Israel

• TV Report Shows Gazan Women Recruits Of The Democratic Front For Liberation Of Palestine (DFLP) Training In Tunnel Warfare, Simulating Taking Over Israeli Armored Vehicle

• Report On Hamas Al-Qassam Brigades' Anti-Tank Unit Claims Unit Is Prepared For An Israeli Ground Invasion, Shows Kornet Missile Simulator

• Al-Mayadeen TV Features Gaza Attack Tunnels Of The Al-Mujahideen Brigades

• Video Featuring Hamas Commando Team Features Tunnels

• Footage Of Tunnels Used By Hamas For Terror Attacks

• Report On Hamas Fighters In Gaza Tunnel

• Report On Hamas Tunnel-Digging Unit

• Saudi Arabia's Al-Arabiya TV Reports On Gaza Tunnels And Missile Production Before Being Ordered By Hamas To Leave Gaza

Palestinian Islamic Jihad (PIJ) Drills Capturing Israeli Soldiers Via Tunnels

• Palestinian Islamic Jihad Showcases Military Capabilities on Iranian TV: It Is Our Natural Right to Capture Israeli Soldiers; We Have New Tunnels

• Palestinian Islamic Jihad Digs New Tunnels In Gaza

Popular Resistance Brigades' Use And Construction Of Tunnels, Trenches, And Fortifications

• Popular Resistance Brigade Construction And Use Of Tunnels

• Popular Resistance Brigade Construction And Use Of Trenches

• Popular Resistance Brigade Construction And Use Of Fortifications

Iran-Backed Militias In Syria Use Tunnels To Transport Arms, Protect Weapons Depots

• Syrian Opposition Media Outlet: Iran-Backed Militias Complete Underground Border Crossing Between Iraq And Syrian Desert To Smuggle Weapons, Drugs Without Fear Of Airstrikes

• Syrian Opposition Websites: Despite U.S. Attacks, Iran-Backed Militias Still Active in Eastern Syria: Commanders Have Returned; Militias Are Digging Tunnels For Weapons, Recruiting Locals

• On Facebook, Syrian Opposition Page Reports Iran Backs Digging Of Tunnels In Syria To Protect Missiles, Weapons Depots, Reveals Presence Of Iranian, Afghan, Iraqi Fighters

• Syrian Opposition Media Outlets: Islamic Revolutionary Guard Corps And Its Militias Excavate Tunnels On Syria-Iraq Border To Evade Air Attacks On Arms Shipments

Harakat Muhajireen Ahl-e-Sunnat Iran Digs Tunnels, Underground Bunkers In Syria

Other Syria-Based Jihadi Groups Building And Using Tunnels, Trenches, And Fortifications

• Other Syria-Based Groups Building And Using Tunnels

• Other Syria-Based Groups Building And Using Trenches

• Other Syria-Based Groups Building And Using Fortifications

Taliban Tunnels In Afghanistan And Pakistan

• Afghan Taliban Tunnels

• Pakistani Taliban Tunnels

 

FOREWORD BY GENERAL (RET) KENNETH F. MCKENZIE JR., USMC

The history of tactical warfare revolves around the concept of finding unassailable flank. A force that can position itself where it can bring unexpected foie and maneuver against an opponent can gain a significant tactical advantage. From the trenches of the first World War until now, this has been the holy grail of tacticians. We've tried it with protected maneuver – the use of tanks; we've tried it with airborne and air-mobile forces, and we've tried it with the expenditure of massive amount of firepower to create gaps in an enemy's defenses. Some of these techniques have worked, and some of them have failed. Now we see for the first time the systematic utilization of highly organized deep tunnel networks to maneuver against a foe. The intent is an old one – to create an assailable flank or a position of advantage against an opponent.

This MEMRI report is timely and disturbing. They have done a remarkable job of exposing the new complexities of combat in a built-up urban area, and also how tunnels add a new and concerning dimension to conflict outside of urban areas. As they demonstrate, we now need to treat ground combat as far more than just tactical interaction on the surface of the earth and in the infrastructure that is above it. We must now consider operations to involve not only fighting on the surface of the earth, but also operations underground in the shallow urban infrastructure, and, of course, operations in the deeply tunneled underground. At the same time, we must be prepared to fight above the ground, and in the urban infrastructure. We are now in an era of genuine multi-dimensional operations.

There are limits to this new approach – it requires that the fight be undertaken on prepared ground, so it is inherently defensive in its application, although tunnels did serve as a method for injecting terrorists into Israel in the early states of the October attack. Solving this problem will require the use of advanced robotics, ground searching radar, and advanced AI. Understanding the complexity of the problem we confront is the first task, and this MEMRI report is precisely what is needed.

General (Ret) Kenneth F. McKenzie Jr., USMC

14th Commander, U.S. Central Command

Introduction

Hamas's October 7, 2023 surprise attack, which included the use of paragliders, the tearing down of the border fence, the taking of hostages, and their transport, along with bodies of the murdered, into the massive network of Hamas's tunnels, was a huge military achievement for terrorist organizations and serves as a model for others to follow in future attacks. As Hamas leader abroad Khaled Mash'al said on October 26, 2023 on Egyptian television: "The Russians told us that what happened on October 7 would be taught in military academies. The Chinese are thinking of carrying out a plan in Taiwan, doing what the Al-Qassam Brigades did on October 7. The Arabs are giving the world a master class."[1]

The construction of at least 300 miles of tunnels right under the noses of Israeli and even U.S. intelligence was a stunning achievement. John Spencer, the Chair of Urban Warfare Studies at West Point's Modern War Institute, outlined the extent of the tunnel network under Gaza on July 1, 2024: "It is growing more and more difficult to describe Hamas's underground network in Gaza as the Israeli military continue discovering tunnels, London metro 402 km, New York subway system 399 km, Seoul metro 340 km. The 'Gaza metro' is believed to be over 500 km but may end up being even bigger."[2] Spencer detailed this issue in a longer article titled "Gaza's Underground: Hamas's Entire Politico-Military Strategy Rests on Its Tunnels."[3] Spencer also wrote, alongside Colonel Patrick Sullivan and Modern War Institute editor-in-chief John Amble, a study titled "Israel's Campaign against Hezbollah and the Fight for Southern Lebanon's Tunnels" in which they concluded: "The fight to control the tunnels and deny their control to Hezbollah is a necessary component of any campaign against the group. A war might not be won exclusively in the tunnels, but it cannot be won without accounting for them."[4]

On February 9, 2025, Hamas released a propaganda video showing Israeli hostages Or Levy, Eli Sharabi, and Ohad Ben Ami being led through tunnels, where they had been held captive for nearly 500 days, to be handed over to Israel. Their release took place February 8. The video, apparently the first footage released by Hamas of hostages walking through the tunnels, gives a glimpse of the tunnels' sophistication and depth underground, and shows the heavy doors and the rooms in which hostages were kept. The information it provides is valuable for clues as to in the tunnels, and gives a glimpse of how elaborate and deep they are, as well as the heavy doors and rooms of the hostages. This is valuable for clues to how and where other hostages may be kept.

Strategic military interest in the issue of terrorist use of tunnels is well founded, as many terrorist organizations are actively using them in combat. Most recently, according to a February 6, 2025 report by the Syrian website Eye of Euphrates, newly constructed tunnels have been discovered in Deir Al-Zour, in eastern Syria, since the fall of the Assad regime. The report stated that the construction of these tunnels had "reached its peak" some six months before the regime's fall.[5]

On January 24, 2025, the independent Syrian Observatory for Human Rights (SOHR) reported on a network of tunnels constructed and used by Iran-backed militias in Deir Al-Zour during the Assad era (to view a video of the tunnels, click here).

Earlier, on December 16, 2024, the Qatar-owned Al-Jazeera TV channel published a video it identified as showing, in Deir Al-Zour, a deserted underground headquarters, including a tunnel dug 50-65 feet deep, that Iran-backed militias and Russia's PMC Wagner had used to plan military operations, including some carried out against U.S. forces and the Syrian Democratic Forces (SDF). The video features Farsi-language documents and a map highlighting the U.S. military base at the Conoco gas field in the area, as well as other U.S. sites in eastern Syria.[6]­­

A video report features a map on the walls of a tunnel identified as showing detailed descriptions of deployments of various military forces in Syria.

O­­­­­n July 6, 2024, the official Telegram channel of Yemen's Ansar Allah Houthi movem­­ent released a video of a "complex" military exercise that showed, among other things, anti-tank squads emerging from underground tunnels.[7]

Click here to view this video produced by the Houthis showing tunnels (at the 1:50 mark). Below are still images from the video:

Houthi fighters emerging from a tunnel.

Detailing how tunnels are being built and used by terror organizations, this study reviews their use for: military exercises, communication and dissemination of data and intelligence; training, transportation and logistics; resupply, storage, and smuggling; weapons manufacturing; infiltration, exfiltration, medical evacuation, and ambushes; maneuvering and flanking enemies and for cover and concealment for fighters; as a firing range; attacking or capturing soldiers; firing mortars and artillery; and for emplacing and deploying concealed multiple launch rocket systems. Jihadi groups often provide contact information, including via WhatsApp, for supporters to send funds for the construction of tunnels and trenches, which, alongside tunnels, jihadis have actively used on many battlefields.

The use of tunnels by adversaries is a longtime worry for U.S. government and military planners, which have invested a lot of time and money, mainly through the Defense Advanced Research Projects Agency (DARPA), to extensively study it and develop technology to deal with this threat. Terrorist use of tunnels is also a U.S. national security issue – and not only because of threats to U.S. embassies and other places of interest, but because tunnels originating in Canada and Mexico constitute a direct threat to homeland security. Further, Israel's inability to take the Hamas tunnels within the past 12 months, due largely to Hamas's use of human shields, will give military strategists much to plan for and in the future, Israel's hard-won expertise will be sought after.

The following MEMRI study, which draws on ten years of terrorist organizations' video productions, online posts, and other reporting, including never-before-seen releases of terrorist activity inside tunnels, reviews how jihadi terrorist groups around the world, including the Islamic State (ISIS), Al-Qaeda Syrian affiliate Hurras Al-Din, Hay'at Tahrir Al-Sham (HTS), Hizbullah, the Houthis, Hamas and its Al-Qassam Brigades, Palestinian Islamic Jihad and its Al-Quds Brigades, the Popular Resistance Brigades in Syria, Iran-backed militias in Syria, Harakat Muhajireen Ahl-e-Sunnat Iran, and other Syria-based jihadi groups, are using tunnels.

It covers the history of Hamas tunnels, including little-known details of how the Muslim Brotherhood helped Hamas, as described by Kuwaiti Islamic scholar and Muslim Brotherhood leader Tareq Al-Suwaidan.

 

The U.S. Military And The Defense Advanced Research Projects Agency (DARPA): Cutting-Edge Tunnel Research

The Defense Advanced Research Projects Agency (DARPA), a Department of Defense (DoD) research and development agency that adapts new technologies for use by the military and is often called the "DOD's think tank," has for years been researching the potential offensive and defensive use of tunnels. DARPA's research in recent years has reportedly included a range of topics related to tunnels, including finding technologies that will rapidly map, navigate, and search subterranean areas[8] and allow for easier exploration and navigation of subterranean areas that are unsafe for humans.[9]

It has also sought information on unused tunnel systems, particularly a man-made environment spanning multiple blocks and having multiple stories, atriums, tunnels, and stairwells that they could use to conduct research and experiments. These tunnels would be used to research technologies that would be used to leverage subterranean areas.[10] DARPA has used AI to analyze ground conditions to determine how to tunnel quickly and efficiently, and minimize deformation in an established tunnel system. This is an area in which Elon Musk's The Boring Company has also conducted research, focusing on tunnel approaches, downhole sensing, and concepts of operations.[11]

On November 21, 2017, in a statement titled "Digging for Ideas to Revolutionize Subterranean Mapping and Navigation," DARPA examined the importance of "subterranean warfare – whether involving human-made tunnels, underground urban infrastructure, or natural cave networks." It stated that "adversaries are increasingly heading underground to circumvent detection," and that in order to "to explore these possibilities, DARPA has issued a Request for Information (RFI) to augment its understanding of state-of-the-art technologies that could enable future systems to rapidly map and navigate unknown complex subterranean environments to locate objects of interest, e.g., trapped survivors, without putting humans in harm's way."[12]

The following month, on December 21, 2017, DARPA announced a Subterranean or "SubT" Challenge to explore "new approaches to rapidly map, navigate, and search underground environments."

A DARPA video promotes its Subterranean Challenge

Fred Kennedy, who was at the time director of DARPA's Tactical Technology Office, said that "[i]nstead of avoiding caves and tunnels, we can use surrogates to map and assess their suitability for use. Through the DARPA Subterranean Challenge, we are inviting the scientific and engineering communities – as well as the public – to use their creativity and resourcefulness to come up with new technologies and concepts to make the inaccessible accessible."[13]

A DARPA video promoting its Subterranean Challenge explains how participants can enter its "Systems" or "Virtual" tracks.

On March 7, 2019, DARPA said that it was seeking "tools to capture underground worlds in 3D." These environments were to include "including human-made tunnels, underground infrastructure, and natural cave networks."[14] According to a April 29, 2019 DARPA statement, following an "Integration Exercise," competitors in the SubT Challenge announced in 2017 were preparing a "Tunnel Circuit" in August 2019 in which "Teams could earn points by accurately locating, identifying, and reporting artifacts placed within the tunnels."[15] An "Urban Circuit" was reportedly held in February 2020[16] and amid the COVID-19 pandemic, a Cave Circuit originally scheduled for November of the same year was held only in virtual format.[17] DARPA announced the winners of the SubT Challenge on September 24, 2021.[18]

A DARPA video promoting its Subterranean Challenge explains how participants will operate in different environments.

DARPA announced, on April 1, 2020, its "Underminer program," under which three teams, from General Electric, the Colorado School of Mines, and Sandia National Laboratories, would develop technologies and solutions surpassing current commercial drilling capabilities. The goal of the project was to "demonstrate the feasibility of rapidly constructing tactical tunnel networks to provide secure logistics infrastructure to pre-position supplies or resupply troops as they move through an area." In particular the project aimed to "merge breakthroughs in horizontal drilling, trenchless boring technologies, and robotics to create a set of systems allowing consistent underground access."[19] The project reportedly sought to build a robot that imitates an earthworm to dig tunnels to resupply troops in combat.[20]

A DARPA video promoting its Subterranean Challenge explains how participants can win prizes of $750,000 or $2,000,000.

On March 31, 2022, DARPA reported that it had completed its Underminer program, and that the effort had "demonstrated the feasibility of rapidly constructing tactical tunnel networks that enable secure, responsive resupply in denied environments." It further said that "Adversaries, peer competitor nations, and allies around the world are building and exploiting tunnels for tactical operations."[21]

Saying on July 22, 2022, that it was seeking a "compact source for powerful subatomic particles to enable new defense and scientific capabilities," DARPA added that the applications for such a source would include "rapidly mapping the location of underground tunnels and chambers hundreds of meters below the Earth's surface."[22]

While it is unclear whether DARPA's cutting-edge research in tunnel warfare has been able to assist in Israel's underground battle against Hamas, it will most likely provide innovative ideas for future battles.

Under The U.S.-Mexico Border, Smugglers Have Used Hundreds Of Tunnels Over Two Decades – And ISIS Supporters Have Noticed

While the U.S.-Mexico border was one of the top issues in the coming presidential election, there has been little discussion of the national security threat of tunnels, which in the future could pose a national security threat. The Hamas October 7 attack and Hamas's use of tunnels should be seen as a warning. Tunnels have been a concern vis-à-vis the security of the U.S.-Mexico border for decades. Former Ambassador to Mexico Chris Landau said on September 13, 2024: "Hamas folks have this tunnel technology and the cartels in Mexico want to take advantage of that kind of technology... This has got to be the Number One national security interest of the United States – to make sure our own borders are secure."[23]

The tunnels on the U.S.-Mexico border have also been connected to designated terrorist organizations. The notorious Los Zetas drug trafficking organization, which smuggles into the U.S. via manmade tunnel systems along the Mexico-U.S. border, has partnered with Hizbullah, which is "forging ideologically promiscuous ties with Colombia's right-wing paramilitary groups and communist guerillas and digging tunnels for drug cartels on the Mexican-American border – the same kinds of tunnel networks it has spent years perfecting along the geographically similar Lebanese-Israeli border.[24]

On September 5, 2023, two users of the encrypted server Rocket.Chat operated by the Islamic State (ISIS) discussed ways to travel into Mexico and Canada. In two posts, one in Arabic and one in English, user "omar.ansari" asked other users for information travelling to Mexico or Canada, explaining that he had seen videos showing Iraqi and Yemeni men illegally crossing the border from Ecuador into Mexico.[25]

It is well known that Mexican cartels are smuggling people into the U.S. On June 20, 2024, it was reported that Mexican drug cartels were offering a special "VIP" package for moving people across the border: For $6,000-$15,000, a cartel will smuggle a person across the border via a tunnel from Ciudad Juárez into El Paso, Texas. According to a senior Mexican official, a joint investigation by Mexican and U.S. authorities found that one cartel has been smuggling at least 1,000 migrants through the tunnels into El Paso every month.[26]

The most recently discovered tunnel from  Juárez into El Paso was discovered January 9, 2025. It was described by U.S. federal officials as "sophisticated" – about six feet tall and four feet wide with lighting and ventilation throughout. It goes under the Rio Grande, the border wall, the American Canal, and levees, and leads to a network of storm drains in El Paso. U.S. officials began filling the tunnel in with cement on the U.S. side about a week after its discovery, and it was reported in late January 2025 that Mexican authorities have begun filling it in on the Mexican side.[27]

Arab-American YouTuber Jad Manon posted a video in Arabic on August 1, 2024 on Arab immigration into the U.S. from Mexico that highlighted the process Arabs must go through in order to cross into the U.S. either legally or illegally. Arabs who are caught crossing into the U.S. illegally can ask for asylum status, he explained, while Mexicans are sent back to Mexico. He said: "There are also people who cross through tunnels they dig underground, or they can saw [through a beam] and go under it, like that Mexican guy showed us, or they climb the wall and go to the other side, to America, and especially to San Diego."[28]

 

To view this clip on MEMRI TV, click here or below

Media reported on May 18, 2023 that Mexican federal agents had found a tunnel under construction, located in a Tijuana home near the border across from San Diego about a mile east of the San Ysidro Port of Entry. The tunnel reportedly stopped about 45 feet away from U.S. soil.[29]

A tunnel uncovered in Tijuana in May 2023.

The U.S. Attorney's Office for the district of Arizona reported on June 24, 2021 that a man had been sentenced to 41 months in prison for conspiracy to import methamphetamine, cocaine, fentanyl, and heroin. The charges were related to the entrance to a tunnel that had been discovered inside his house.[30]

A tunnel uncovered by federal agents of the San Diego Tunnel Task Force uncovered a "sophisticated drug smuggling tunnel" on March 19, 2020. It extended over 2,000 feet underground from a warehouse in Tijuana, Mexico to a warehouse in a commercial complex in the Otay Mesa area of San Diego. Agents seized cocaine, methamphetamine, heroin, marijuana, and fentanyl from the tunnel, with a total street value estimated at $29.6 million.[31] On April 10, 2020, the U.S. Attorney's Office for the Southern District of California reported that a Mexican national with legal residency in the U.S. had been charged with trafficking $30,000,000 worth of the drugs via the tunnel.[32]

A report on April 20, 2016 by the U.S. Attorney's Office for the Southern District of California stated that federal officials had seized what was thought to be the longest cross-border tunnel ever discovered along the California-Mexico border up to that time, with an estimated length of about 2,400 feet. Also confiscated was over a ton of cocaine, in the single largest cocaine seizure associated with a Southern California tunnel at the time. The tunnel, which stretched from a house in Tijuana, Baja California, Mexico to an outdoor fenced-in commercial lot in an Otay Mesa industrial park, had rail and ventilation systems, lights, and a sophisticated large elevator leading from the tunnel into a closet inside the Tijuana residence.[33]

On March 23, 2016, the U.S. Attorney's Office for the Southern District of California reported that Federal officials had seized a cross-border tunnel and arrested four people in Calexico, California and Arizona, and had confiscated over a ton of marijuana. The tunnel, which was 415 yards long, stretched from a restaurant in Mexicali, Mexico to a house in Calexico, California, about 300 yards north of the international border. In the front room of the residence, agents found a hole in the floor covered with tile leading to a shaft leading underground.[34]

A tunnel approximately 600 yards in length, was discovered in April 2014 following a five-month probe. It connected a commercial building in Otay Mesa with a warehouse in Tijuana. The passageway was equipped with lighting, a crude rail system, and wooden trusses and was accessed down a 70-foot shaft secured by a cement cover. The U.S. Attorney's Office for the Southern District of California reported on April 6, 2014, that a second defendant had been charged in connection with this tunnel.[35]

U.S. Customs and Border Patrol reported in 2017 that more than 200 smuggling tunnels had been discovered along the U.S.-Mexico border in various stages of construction, with 120 of them found in Nogales, Arizona. Border Patrol Agent Felipe Jimenez joked that "one of these days the whole city is going to drop 15 feet because there are so many tunnels." Terrorist organizations have noticed this vulnerability; an ISIS magazine depicted smugglers bringing a nuclear device into the U.S. using a tunnel from Mexico.[36]

On February 12, 2013, U.S. Immigration And Customs Enforcement reported that Federal authorities had shut down a recently completed, cross-border drug smuggling tunnel and seized more than 1,200 pounds of marijuana. This followed a multi-agency investigation by the Nogales Tunnel Task Force, with significant assistance from U.S. Customs and Border Protection Border Patrol in Nogales. The hand-dug tunnel was about 68 feet long and averaged about two feet wide. The entrance was in the front yard of a private residence in Nogales and ran for about 26 feet underground before passing under the international boundary and running 42 feet on the U.S. side of the border. Since 2010, authorities had shut down 26 tunnels in Nogales. [37]

A tunnel shut down by the Nogales Tunnel Task Force (source: Ice.gov)

A May 2008 document from the National Drug Intelligence Center stated that about 33 tunnels had been discovered along the California-Mexico border since 1993, and that 21 of had been discovered since 2006 alone.[38] A DHS "Master List of Border Tunnels" dated December 19, 2007 lists 21 tunnels from California to Mexico.[39]

A Look At Canada-U.S. Tunnels

While the U.S.-Mexico border appears to be a greater national security concern, little thought has been devoted to the tunnels running from Canada to the U.S. On July 21, 2005, the U.S. Attorney's Office of the Western District of Washington reported the arrest of three men in connection with the construction of "a sophisticated tunnel running from British Columbia, Canada, into Washington State." The tunnel, at a depth of between three and 10 feet, was about 360 feet long and was reinforced with wood and steel. The men charged with crimes related to distributing and importing marijuana. U.S. Attorney John McKay said about the case: "The presence of a tunnel on our northern border threatens the security of both countries, whether it is used to smuggle drugs, contraband or even terrorists." The tunnel, reportedly the first ever discovered between Canada and the U.S., [40] had cost $1-$6 million to build.[41] It was destroyed and in 2006 the men were sentenced to nine years in prison.[42]

Islamic State (ISIS) Used Tunnels In Iraq, Syria, And Afghanistan; Publications Instruct On And Encourage Tunnel Construction

During the time when it was most active, the Islamic State built tunnels in Iraq and in Syria. Tunnel and cave systems constructed by the Islamic State were found in northern Iraq, including a 1,300-foot tunnel in Ninawa Province and another in Mosul. An estimated 3,000 fighters were at one point reportedly hiding in tunnels the group built in Syria. It has also been pointed out that ISIS leaders, including Abu Bakr Al-Baghdadi, have been found hiding in tunnels. Pro-ISIS publications have encouraged readers to dig secret tunnels to prepare for a coming war and giving instructions on how to dig tunnels.

ISIS Supporter Shares Tunnel-Building Manual Based On Work Of ISIS Supporter In Gaza

On February 26, 2024, a user of ISIS-operated server on Rocket Chat shared a manual by pro-ISIS Al-Saqri Foundation For Military Sciences providing instructions on how to build tunnels used for military and smuggling purposes. The manual is based on the memoirs of one Jarrah Al-Ansari, an ISIS supporter in the Gaza Strip, who describes the use of tunnels in warfare as an especially effective means in reaching secure locations and smuggling food, supplies, vehicles, and weapons to a designated area, or as prison facilities.[43]

The manual included photos describing a typical tunnel, beginning with the opening, called "the well" by Gazans, and going on the "elbow," where the tunnel well curves at a certain depth to head to the target area. According to the description, there are two types of wells, vertical or slanted, and in this case, they are used for smuggling cars and equipment. Then comes the "tunnel line" and finally the "eye," from which the tunnel exits to the target area or location.

An improvised process for removing sand from tunnels during excavation.

ISIS Tunnels Discovered In Iraq

On November 2, 2019, it was reported that the Operation Inherent Resolve (OIR) anti-Islamic State (ISIS) coalition had uncovered several ISIS tunnel systems in northern Iraq. OIR used demolition material to destroy a 1,300-foot tunnel in Ninewa Province. Two other tunnel systems were destroyed as well. It's believed that the tunnels served as "bed down locations" for terrorists and were a transit hub for ISIS fighters.[44]

The British Elite Special Forces snipers launched in late July 2020, an attack on jihadis hiding in mountain caves in Iraq, killing 100 IS fighters. Since April 2020, there have been approximately ten battles in northern Iraq and Syria. The Islamic State maintains a network of caves and tunnels in northern Iraq where its fighters have been able to hide and avoid capture.[45]

Media reported on March 2, 2017, that the Islamic State had built a tunnel hiding a training camp in Mosul, Iraq. The training camp was almost a mile long and was found 32-feet underground.[46] Additionally, it was estimated to hold more than 150 fighters at a time. It was described as being a "well-equipped facility" and was the largest ISIS camp discovered so far.[47]

An Iraqi soldier in an ISIS training facility located 22 feet underground.

A network of underground tunnels was reportedly discovered by Kurdish forces in Iraq on March 4, 2016. Chambers were thought to be 30-feet deep, allowing ISIS fighters to protect themselves from airstrikes. Additionally, the soldiers investigating the tunnels found that the chambers had electricity.[48]

The United States' forces were reported on April 29, 2020, to have successfully destroyed an Islamic State cave system in Iraq with airstrikes. The airstrikes hit 10 caves and were conducted in coordination with Iraqi forces. It was estimated that between five to 10 ISIS fighters were killed in the attack. Moreover, ISIS documents, devices, and equipment were recovered from the caves. Major General Eric hill, the commanding general for Operation Inherent Resolve, noted that coalition forces are targeting ISIS with "relentless pressure."[49]

ISIS Tunnels Discovered In Syria And Afghanistan

Between 2016 and 2019, there were many reports of the Islamic State (ISIS) using tunnels in Syria and Iraq. On February 14, 2019, a group of Islamic State jihadis used tunnels and suicide bombers to defend their final square kilometer in eastern Syria. The estimated number of fighters was around 1,000. U.S. forces in the area carried out airstrikes in addition to having forces on the ground, all searching for jihadis.[50]

On March 4, 2016, it was reported that a network of underground tunnels was discovered by Kurdish forces in Iraq. Chambers were thought to be 30-feet deep, allowing ISIS fighters to protect themselves from airstrikes. Additionally, the soldiers investigating the tunnels found that the chambers had electricity.[51]

There were reports on December 4, 2018, that there were up to 3,000 ISIS soldiers thought to be hiding in tunnels and bunkers in Syria and Iraq. A senior security source noted "Islamic State fighters have retreated to well-strengthened underground networks in the desert." Additionally, Army Colonel Sean Ryan stated that it was difficult to know how many jihadis there were as ISIS was underground.[52]

The Syrian Democratic Forces (SDF) were reported in February 2019 to have been slowed in their effort to defeat the last pocket of ISIS in Syria by the group's "extensive use of tunnels and human shields." Mustafa Bali, an SDF spokesman stated "It is expected that there are still undiscovered tunnels, even rooms underground...this creates a military problem for us."[53]

On April 13, 2017, U.S. Forces in Afghanistan struck an ISIS tunnel complex in Achin district, Nangarhar province, Afghanistan.[54] This reportedly involved the largest non-nuclear bomb ever used in combat.[55]

ISIS Publications Encouraging And Instructing On Digging Tunnels

Pro-ISIS Al-Burhan media, in a July 10, 2020 graphic, advised the mujahideen in the Indian Subcontinent to dig tunnels in preparation for a coming war and to be secretive about these preparations.[56]

Pro-ISIS media encouraging secret tunnel construction.

The pro-ISIS Al-Saqri Foundation published on November 14, 2018, a pamphlet describing how to dig tunnels for military use, written by a Jarrah Al-Ansari.[57]

Pro-ISIS media teaching readers how to dig tunnels.

Hurras Al-Din, The Al-Qaeda Affiliate In Syria, Digging Trenches, Fortifications

Al-Qaeda's affiliate in Syria Hurras Al-Din has for years been digging trenches and fortifications in Syria. The group released on September 18, 2019, a pictorial report showing its fighters on guard duty, digging trenches, and stationed at posts.[58]

Hurras Al-Din pictorial report showing fighters in trenches.

Hurras Al-Din media arm Sham Al-Ribat published on August 6, 2019, a pictorial report showing the group's fighters at their positions on the front lines in Aleppo, Latakia, and Hamah areas digging fortifications and aiming weapons at enemy forces.[59]

  
Hurras Al-Din pictorial report shows fighters digging fortifications.

Hay'at Tahrir Al-Sham (HTS) Uses Tunnels For Defense Against Airstrikes, As "Terrifying Examples For The Enemies," And A "Popular Culture"

Hay'at Tahrir Al-Sham (HTS), a jihadi group that formed in Syria in January 2017 as a merger of six other groups, has used tunnels in Syria. Posts from their outlets and leaders have shown fighters digging tunnels and encouraged others to do the same, emphasizing their defensive value against airstrikes. They have referred to the tunnels as "terrifying examples for the enemies" that have become a "popular culture" in Syria. They have also described Russian efforts to destroy tunnels. HTS fighters have made use of trenches and fortifications as well. It should be noted that following the HTS-led takeover of Syria in late 2024, HTS leader Abu Muhammad Al-Joulani became de facto leader and then president of Syria in January 2025, reverting to his given name Ahmed Al-Sharaa. 

HTS Halts Syrian Military Through Use Of Defensive And Offensive "Explosive Tunnels"

On August 28, 2023, the pro-HTS Murasil Maydani Telegram channel published a series of posters detailing recent confrontations between HTS' Al-Fath Al-Mubin Operations Room and the Syrian military in the village of Al-Milajah, south of Idlib. The text on the posters state that the Syrian military tried three times to advance in the front, and were three times repelled by the rebels by means of artillery, rockets, and mortars, as well as the detonation of "explosive tunnels." The posters emphasize the defensive and offensive effectiveness of tunnels rigged with explosives, and gives examples of their use against Syrian regime forces over the past several years.[60]

In one poster, HTS claims that the use of tunnels "has been an effective tactic in the Syrian war, by means of which many achievements were attained such as the liberation of areas, caserns, as well as a means of attrition and terror for enemy soldiers... Detonating explosive tunnels remains one of the most effective tactics both in defens­e and offense positions, given their low cost and the significant impact it creates."

HTS poster describing the use of tunnels as an effective tactic in the Syrian war.

HTS poster describing the use of tunnels as an effective tactic in the Syrian war.

On May 5, 2019, Dr. Bassam Sahyouni, head of the HTS-affiliated Shura Council of the General Conference of the Syrian Revolution, stated that the military strategy of digging tunnels is one of the most successful tactics in the history of warfare and urges fighters in Syria to make of digging tunnels a "popular culture," noting the tactic's effectiveness in Vietnam, Afghanistan, Bosnia, Palestine, and Syria.[61]

HTS official describing tunnel use as an effective tactic and a "popular culture."

HTS: Gaza Owes Its "Legendary Steadfastness" To Tunnels

HTS media outlet Ebaa' news agency released on September 30, 2019, a three-minute and 40-second animation titled "The Culture of Fortification: A Military Strategy" ­highlighting the importance of tunnels, trenches, and shelters in combat. After providing historical examples of battles in which trenches had been used, the video considered Gaza as an ideal example of a well-fortified city.[62]

An HTS animation highlights the importance of tunnels, trenches, and shelters. Bottom left caption reads: "Gaza is renowned for its tunnels and trenches."

 

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* Steven Stalinsky, Ph.D., is Executive Director of MEMRI; R. Sosnow is Lead Editor at MEMRI; A. Smith is a Research Fellow at MEMRI; Z. Emile, K. Choukry, Matt Schierer, N. Mozes, Y. Kerman, N. Shulder, and A. Goren are JTTM Researchers.