The Army Is Preparing to Go Underground

Story Stream
recent articles

As the Army prepares for the future battlefield, it is investing time, money, and effort into fixing a critical readiness gap—soldiers' ability to fight underground. American soldiers must be able to engage the enemy in dark, damp and tight spaces underground. These environments can include complex tunnel and bunker networks that severely challenge traditional communications, maneuver, sustainment and situational awareness.

Just like fighting in extreme cold weather or the jungle or the mountains, subterranean warfare requires its own set of tactics, techniques and procedures, and specialized equipment and training. To meet this challenge after almost two decades of above-ground counterinsurgency warfare, the Army is moving forward with developing tactics, designing training programs, building facilities, acquiring, developing and testing equipment and establishing doctrine to rectify this readiness gap.

Why Prepare to go Underground?

Subterranean environments are ubiquitous across the threat environment and terrain. Hostile actors evade and attack from underground networks that challenge Soldiers’ ability to engage the enemy. The Army must prepare for an underground element when countering each adversary designated in the 2018 National Defense Strategy; from near-peers Russia and China to rogue states like Iran and North Korea and violent extremist organizations. The Army can encounter subterranean environments in rural tunnels and cave complexes or dense urban sewer or subway systems as well as hardened underground military sites. Although varying in type, all underground environments mitigate U.S. technological superiority.

How the Army is Preparing


The Department of Defense provides specific guidance to U.S. forces in the jungle, mountainous, and urban environments. Only sparse resources address subterranean operations. Army field manuals refer to subterranean elements only as specific elements of urban environments such as basements, sewers and subways. (FM 30-21-21 Chapter 6). It does not address rural tunnels, cave complexes, underground bunkers, smuggling tunnels, enemy tactical tunnels, and whatever underground complexes adversaries create. This is inadequate for future planning.

The Army prepared its first doctrinal publication related to subterranean warfare, Training Circular TC 3-21.50: Small Unit Training in Subterranean Environments, through an urgent development process in November 2017, and authorized it for immediate implementation. This document updated practices that barely changed since the early 1990s, Military Times reported. One key conclusion to expect little to no communication, necessitating operating upon understood intent. (South 2019). notes that in the past, subterranean missions were given to special operations units like the Army's 75th Ranger Regiment. Renewed focus on great power competition and increased tensions with North Korea is forcing the Army to expand subterranean expertise to regular units with enough manpower to control large subterranean complexes. (Cox 2018).


The Army has increased subterranean training for regular units at the tactical level. Military Times explains that for strategic reasons, Army leadership has been tight-lipped regarding upper echelon strategic planning. (South 2019).

Fort Benning Maneuver Center of Excellence is leading tactical subterranean training. Citing future urban operations, its commandant, Colonel Hedrick, emphasized the need for Soldiers to familiarize themselves with operating in the subterranean element, including sewers and subways. The goal is for units to be able to conduct subterranean training at home stations in above ground maze-like structures, built from shipping containers, that will simulate realistic underground conditions.

U.S. ground forces also conduct tactical subterranean training with experienced international partners. In 2018, Marines trained with Israeli and Norwegian troops during the Juniper Cobra drills. (Ahronheim 2018).

According to the Army website, the Army Combat Capabilities Development Command led U.S. Army Subterranean and Dense Urban Environment Materiel Developer Community of Practice in three workshops to explore the challenges of fighting underground. (Calloway 2019).


The Army is spending $572 million to prepare 26 out of its 31 active combat brigades for subterranean operations. notes that much of these funds will go towards acquiring equipment for tunnel and bunker detection, neutralization, breaching, maneuver, fires, breathing, communication, optics, protection, sustainment, intelligence, surveillance and reconnaissance, and mapping. (Cox 2018).

The Joint Improvised-Threat Defeat Organization is working with the Army Engineer Research and Development Center to detect subterranean facilities. Border Tunneling Activity Detection System-Point uses buried geophones to listen for construction. Active Detection Systems use seismic tools to search for existing facilities. The center is also experimenting with aerial drones to detect changes in the magnetic field over a wide area. Many of these systems are currently deployed in the U.S. and overseas. (Harper 2018). In 2018 the Israel Defense Forces fielded a mobile laboratory that has successfully located five tunnels along the Israel-Gaza border. (Helmhold 2018).

It is often optimal for destroying or sealing underground threats. In rural settings, the safest and most efficient option might be to collapse the tunnel from the air, for example, dropping the MOAB on ISIS tunnels and caves in Afghanistan. In more populated areas this tactic might cause unacceptable collateral damage. In Israel’s 2014 Operation Protective Edge, engineering units initiated controlled demolition of Hamas tunnels in the Gaza Strip. In 2018, Israeli forces permanently sealed tunnels that crossed its border from Lebanon by flooding them with concrete. (Magid and TOI Staff 2018). Modern War Institute Chair retired Major John Spencer, advocates equipping units with quick-forming foam to temporarily seal underground passageways. (Spencer 2017).

Units fighting underground need to breach reinforced structures. Breaching equipment includes tools with a variety of attachments and torches to cut through metal. Sledgehammers, pry bars, and battering rams are essential. (South 2019). The Army is testing the TEC Torch can operate underground and even underwater. It would allow Soldiers to cut through locks, bolts, cable, and other obstacles, burning for a few seconds at nearly 4,000 degrees Fahrenheit. (Havranek 2019).

Maneuver, communication, and shooting are challenged underground. Guide ropes help first responders operate in sewers and underground transportation hubs. A National Interest article claims that the Army wants its tunneling tools so that troops can create their own entrances, exits and pathways. (Peck 2019). In underground environments long, unwieldy rifles are suboptimal. Instead, the Modern War Institute advocates troops carry submachine guns with a flashlight attachment. (Mills 2019).

Training and Doctrine Command Chief General Townsend noted that units lose communications even one floor underground. The Army is looking at the handheld MPU5 smart radio to build a mobile ad hoc network using a portable WiFi repeater to connect subterranean soldiers to a commander who can track their movement from above ground.

The subterranean Training Circular states that Soldiers must carry a breathing apparatus. Current equipment runs up to $13,000 apiece and may give troops less than 40 minutes of breathing. Special operations versions with filters can give them more time. A device to detect poor air quality can allow troops to use breathing apparatuses more efficiently.

Subterranean environments often have zero illumination, rending standard night vision ineffective. The new Enhanced Night Vision Goggle B uses thermal imaging that does not require illumination, making it ideal. The Army began two-week long field evaluations in April 2019. Over the next two years, 10,000 soldiers and 3,100 Marines will receive the goggle which was developed by PEO Soldier with the Soldier Lethality Cross Functional Team. This is the first product to emerge from Army Futures Command and will be given first to units deploying to Korea, where the subterranean threat is salient. (Cox 2019).

The Army is looking at throwable robots like the First Look 110 and the PackBot 510, to conduct surveillance and detect chemical threats. The Army’s Rapid Equipping Force requested off-the-shelf technology that can map tunnels in real-time. The equipment must be portable and able to operate in a GPS-denied environment. Army Contracting Command wants prototypes by May 15, 2019, and could make a ­purchasing decision within months. (Inside Unmanned Systems 2019).

Robots can solve logistics problems as well, potentially delivering supplies to an underground point of need. A robot that moves ahead of troops with a shield and sensors could provide the necessary protection, situational awareness and in some cases fire. Underground tunnels provide minimal cover. Units will need ballistic shields like those used by SWAT teams. Noise from discharged weapons is amplified underground, necessitating suppressors and hearing protection.

The National Interest notes that the U.S. military wants to develop offensive tunneling capabilities. DARPA’s fifteen-month, $11 million Project Underminer aims to rapidly construct tactical tunnel networks to create secure logistics infrastructure, enabling the pre-positioning of supplies. The Army's Multi-Domain Operations concept envisions facing peer rivals able to strike the strategic support area, necessitating dispersed and hardened logistics. Tactical tunnels would obviate reliance upon forward operating bases and vulnerable supply lines that sustain them. (Peck 2019).

Insights and Suggestions

The Army understands the need to enhance regular units with subterranean capabilities. The first step is to update the subterranean Training Circular 3-21.50 into an official doctrinal publication. The Army should develop a school dedicated to subterranean warfare while incorporating subterranean training into existing schools. Finally, the Army still needs to field optimized gear. The Army should increasingly leverage international partner, first-responder, industry, and science community expertise. Israel has substantial experience in detecting, destroying, and fighting in underground tunnels. Mining and construction companies and geologists have significant subterranean experience as well. Subterranean detection methods should utilize an array of methods, including specialized geological technology, human informers, and surface surveillance. Finally, it is critical to consider the psychological effects of fighting underground in dark, isolated, and confined places and to train and develop tactics, techniques and procedures accordingly. (Richemond-Barak 2018).

Jeremiah Rozman is a national security analyst at the Association of the U.S. Army. He served as an infantry point light machine gunner in the Israel Defense Forces and is a doctoral candidate at the University of Virginia studying international relations.

Show comments Hide Comments