The contemporary battlefield is no longer confined to the surface. It has expanded into the complex subterranean realm, where adversaries skilfully exploit these hidden spaces to nullify the technological advantages typically held by more conventional forces. From antiquity to the modern day, subterranean strategies have provided militarily inferior actors with a potent means of countering conventional strength.[1]
Nowhere is this trend more visible than in the Middle East, where underground tunnel networks have become an indispensable component of hybrid warfare tactics employed by non-state actors such as Hamas, Hezbollah, and the Houthis. Far from being mere relics of siege warfare, these networks are multi-functional military assets designed for concealment, resilience, and strategic deception. While they form only one part of broader hybrid doctrines, underground infrastructures today allow asymmetric forces to project power, survive high-tech assaults, and disrupt the tempo of conventional military campaigns.[2]
The History of Underground Warfare: From the Viet Cong to Hamas, Hezbollah and the Houthis
From Roman and Ottoman siege tactics to the dramatic mine detonations at the Battle of Messines in World War I, and the guerrilla tunnel systems of the Viet Cong, tunnel warfare has historically served both offensive and defensive roles. The Viet Cong’s Cu Chi tunnels stretched up to 320 kilometres and served multiple functions during combat. They were used as hiding spots, communication and supply routes, clandestine hospitals, food and weapon caches, and living quarters for numerous North Vietnamese fighters. The tunnels were instrumental in allowing the National Liberation Front (NLF) guerrillas to maintain a significant presence near Saigon, proving crucial in their resistance against American and Army of the Republic of Vietnam (ARVN) forces.[3]
Its continued relevance today highlights a crucial point: underground warfare is not defined by specific technology, but by its ability to negate superior force through concealment, surprise, and adaptability. Hamas’s network of over 450 miles of tunnels, nicknamed the “Gaza Metro,” is the best modern example of underground warfare. Hamas uses their tunnels for command-and-control to as well as for smuggling, launching ambush operations, and detaining hostages. These tunnels are often reinforced, booby-trapped, and deliberately built beneath civilian infrastructure, not only to shield operatives from Israeli airstrikes but also to complicate enemy rules of engagement.[4] In the October 2023 conflict, despite Israeli air superiority and precision-guided munitions, the tunnels enabled Hamas fighters to sustain operations deep into Israeli territory, demonstrating the capacity of underground networks to reshape battlefield dynamics.
Hezbollah’s tunnel systems along the Lebanese-Israeli border are less publicized but equally strategic. Inspired partly by North Korean engineering, these rock-carved bunkers and cross-border tunnels provide resilience and mobility. Operation Northern Shield, which exposed and destroyed several Hezbollah tunnels in 2018, revealed how long such infrastructure can remain undetected, even by a state like Israel with advanced ISR (intelligence, surveillance, reconnaissance)capabilities.[5]
In Yemen, the Houthis have turned the country’s mountainous terrain into a subterranean fortress. Since 2022, they have expanded “underground military cities” that house leadership compounds, missile factories, radar units, and unmanned aerial vehicle production facilities. These sites are often located 7–10 stories below ground and concealed beneath innocuous structures. With assistance from Iranian and Hezbollah experts, the Houthis have built underground systems that have enabled them to withstand years of coalition airstrikes, even as they mount increasingly sophisticated attacks, including the recent targeting of commercial shipping in the Red Sea.[6]
Tunnel Vision: The Tactical Advantages and Strategic Implications of Underground Warfare
Underground networks shift the operational environment in profound ways. They limit the effectiveness of ISR tools such as drones and satellites, degrade the utility of airstrikes, and force conventional forces into slow, attritional ground operations. Subterranean facilities enable command-and-control continuity, allow ambushes and retreat via hidden routes, and neutralize many of the key advantages — speed, precision, and situational awareness — that modern militaries depend upon.[7]
These networks also form a foundation for hybrid strategies. Hamas, for example, uses tunnels to protect rocket launchers and fighters who surface briefly to strike, then disappear. Hezbollah’s tunnel-borne mobility enables rapid repositioning and psychological pressure on Israeli border communities. For the Houthis, tunnels serve as both sanctuary and logistical lifeline, allowing them to continue operations under fire and move weapons and supplies.[8]
Unlike static above-ground installations, tunnels are difficult to locate, map, and destroy. This forces conventional militaries to either engage in risky ground operations or accept a degree of strategic opacity, both of which favour the underground actor. Tunnel warfare also allows insurgent groups to “shape” the battlefield from below, controlling the timing and location of engagements while denying the enemy decisive victories.
Fighting underground presents unique challenges that even the most technologically advanced militaries struggle to overcome. Subterranean operations involve close-quarters combat in dark, oxygen-deprived, booby-trapped environments. Communication is limited, GPS is ineffective, and standard tactics break down in tight, single-file corridors. The psychological strain, claustrophobia, sensory deprivation, and threat of hidden Improvised Explosive Devices, is debilitating even for elite troops.[9]
In Gaza, Mosul, and Raqqa, it became clear that tunnel networks prolong campaigns, complicate post-combat stabilization, and force militaries to incur higher casualties. They impose a “doctrine-breaking” effect. Conventional forces must abandon their preferred methods and instead adopt slower, more dangerous approaches, often with limited operational payoff.[10]
Tunnel Rats and Technology: How Traditional Militaries are Countering Subterranean Ops
Addressing the tunnel threat requires a multi-layered approach. One of the key technological solutions involves tunnel detection systems, such as ground-penetrating radar (GPR), seismic sensors, and electromagnetic induction devices. While these technologies have advanced significantly, their deployment is often constrained by terrain, cost, and the learning curve of interpreting complex underground environments.[11]
Urban combat training must also be revamped to account for subterranean operations. This includes training troops in tunnel clearing, close-quarters combat in confined spaces, and the psychological endurance needed to operate underground. Specialized units such as the United States Army’s “Tunnel Rats” in Vietnam, or more recently Israel’s Yahalom unit, serve as models for how militaries can build underground combat competencies.[12]
The use of robotics and drones is emerging as a promising frontier. Ground robots equipped with thermal imaging, LIDAR (Light Detection and Ranging), and chemical sensors can enter tunnels deemed too dangerous for humans. Miniature drones can map underground passages and detect explosives, though GPS-denied environments limit their effectiveness. Robotic platforms and drones, such as Israel’s Lanius quadcopters or U.S. throwbots, are now tasked with mapping, surveillance, and even explosive neutralization in tunnels. These tools reduce soldier exposure and provide situational awareness in GPS-denied environments.[13]
Other counter-tunnel strategies are being explored and refined. Historically, flooding an adversary’s tunnels has been employed as a tactic, but recent attempts by the IDF to flood Hamas tunnels with seawater have yielded minimal impact. It took weeks for even small tunnels to fill, with water often draining away due to porous linings and built-in drainage holes. Flooding has proven to be too time-consuming and largely ineffective as a primary method for neutralizing extensive tunnel networks.[14]
The persistent challenge posed by tunnels often stems not from technological gaps, but from strategic underestimation. Prior to Israel’s Operation Protective Edge (2014), key security decision-makers were seemingly unaware of the scope of Hamas’s tunnel threat. Similarly, the U.S. military in Iraq and Syria lacked an integrated subterranean doctrine, allowing ISIS tunnel systems to thrive under major cities. Political leaders, too, often fail to allocate resources or attention to threats perceived as peripheral, until they erupt into strategic surprises.[15]
Tunnel warfare is not confined to Gaza or southern Lebanon. It is spreading into new theatres. Inadequate investment in detection, training, and hybrid threat analysis risks strategic stagnation. Policymakers must integrate subterranean awareness into broader defence planning, particularly in urban, mountainous, or insurgency-prone areas.
Rethinking the Battlespace
Tunnel warfare is not a niche tactic. It is a dynamic domain of strategic importance. Underground networks empower non-state actors to endure, strike unpredictably, and challenge state militaries on their own terrain. They are both a physical threat and a doctrinal disruptor, rendering many traditional military strengths irrelevant.
Countering this threat requires more than brute force, it demands intelligence-driven, technologically integrated, and doctrinally flexible responses. As hybrid conflict deepens in the Middle East and beyond, the battlefront is no longer defined by land, air, and sea. It now includes the earth beneath our feet.
Disclaimer:
The views and opinions expressed in the INSIGHTS publication series are those of the individual contributors and do not necessarily reflect the official policy or position of Rabdan Security & Defense Institute, its affiliated organizations, or any government entity. The content published is intended for informational purposes and reflects the personal perspectives of the authors on various security and defence-related topics.
[1] Gore, Punit Shyam, ‘The Emerging Relevance Of Subterranean Warfare’, March 8, 2024, Bharat Shakti, The Emerging Relevance Of Subterranean Warfare - Bharat Shakti
[2] Ruthven, Sara, ‘Iran's proxies could go 'underground' to gain new advantage, nominee for Centcom chief says’, June 24, 2025, The National, Iran's proxies could go 'underground' to gain new advantage, nominee for Centcom chief says | The National
[3] Marchal, Alexander, ‘Tunnel of CH Chi: how the Viet Cong did to build these tunnels against the USA’, January 28, 2025, Tunnel of CH Chi: how the Viet Cong did to build these tunnels against the USA
[4] Knudson, Jacob, ‘What to know about Hamas' tunnel system beneath Gaza’, January 17, 2024, Axios, Gaza's underground tunnels: What to know as Israel-Hamas war rages
[5] Bassam, Leila and James Mackenzie, ‘Hezbollah's tunnels and flexible command weather Israel's deadly blows’, Reuters, September 27, 2024, Hezbollah's tunnels and flexible command weather Israel's deadly blows | Reuters
[6] Yemen Monitor, ‘Exclusive: Hidden Deep Underground – The Houthis’ Most Secret Warehouses and Factories’, October 30, 2024, Exclusive: Hidden Deep Underground - The Houthis' Most Secret Warehouses and Factories - Yemen Monitor
[7] Richemond-Barak, D., & Voiculescu-Holvad, S. (2023), ‘The Rise of Tunnel Warfare as a Tactical, Operational, and Strategic Issue’, Studies in Conflict & Terrorism, 1–20. https://doi.org/10.1080/1057610X.2023.2244191
[8] Harrison A., ‘Underground Warfare. By Daphné Richemond-Barak. New York, New York: Oxford University Press, 2018. Pp. xxii, 296. Index’, American Journal of International Law. 2020;114(1):178-183. doi:10.1017/ajil.2019.78
[9] Richemond-Barak, D., & Voiculescu-Holvad, S. (2023), ‘The Rise of Tunnel Warfare as a Tactical, Operational, and Strategic Issue’, Studies in Conflict & Terrorism, 1–20. https://doi.org/10.1080/1057610X.2023.2244191
[10] Springer, Paul J. ‘Fighting under the Earth: The History of Tunneling in Warfare’, Foreign Policy Research Institute, April 23, 2015, Fighting Under the Earth: The History of Tunneling in Warfare - Foreign Policy Research Institute
[11] The Economist, ‘How to detect the enemy when they are underground’, June 24, 2021, How to detect the enemy when they are underground
[12] Head, William, ‘How “Tunnel Rats” Fought the Viet Cong in Underground Tunnels in Vietnam’, historynet, June 3, 2023, The Enemy Below the Earth: The Viet Cong Utilized a Vast Network of Tunnels to Fight the Enemy
[13] Baraniuk, Chris, ‘Swarms of Mini Robots Could Dig the Tunnels of the Future’, WIRED, August 11, 2022, Swarms of Mini Robots Could Dig the Tunnels of the Future | WIRED
[14] Lawal, Shola, ‘How Israel’s flooding of Gaza’s tunnels will impact freshwater supply’, Aljazeera, February 3, 2024, How Israel’s flooding of Gaza’s tunnels will impact freshwater supply | Israel-Palestine conflict | Al Jazeera
[15] Spencer, John W. ‘Facing Our Underground Nightmares: Casting Light on the Subterranean Fight’, Association of the United States Army, August 20, 2019, Facing Our Underground Nightmares: Casting Light on the Subterranean Fight | AUSA
