In the aftermath of the outbreak of open hostilities between Israel and Palestinian militia groups based in the Gaza Strip on October 7, the Israel Defense Forces were simultaneously engaged in an escalating series of skirmishes with militia of the Lebanese political party Hezbollah on their northern border. Ongoing clashes have seen Israeli aviation target militia positions and population centers in southern Lebanon, including using white phosphorus munitions and on January 8 killing a Hezbollah field commander. Hezbollah units have meanwhile frequently launched anti-tank missiles on Israeli armor, targeted Israeli Iron Dome air defense systems with artillery, and on January 6 struck a key Israeli mountain airbase with artillery rockets.
Escalating hostilities have fueled growing calls within Israel for a full-scale assault on southern Lebanon. However, with Hezbollah’s military capabilities and firepower being orders of magnitude greater than those of Gaza-based Palestinian militia groups, the feasibility of such action has repeatedly been brought to question both in Israel and in the United States. According to the Washington Post, a secret assessment by the U.S. Defense Intelligence Agency (DIA) warned that Israeli forces would find it “difficult to succeed” in such an operation.
The Washington Post further observed, on the basis of information from multiple U.S. officials, that a “full-scale conflict between Israel and Lebanon would surpass the bloodshed of the 2006 Israel-Lebanon war on account of Hezbollah’s substantially larger arsenal of long-range and precision weaponry.” Speaking anonymously, officials warned Hezbollah’s sizable and increasingly sophisticated missile arsenal would also enable it to seriously threaten Israeli petrochemical plants and nuclear reactors. As a result, the Post reported: “In private conversations, the [Biden] administration has warned Israel against a significant escalation in Lebanon.”
The growing possibility of a major war has drawn attention to the sources of Hezbollah’s power, which have allowed it to confront and largely deter a leading regional military. In particular, its vast network of underground tunnels and bunkers is among the best-fortified in the world and stretches across much of southern Lebanon. This network was key to Hezbollah’s ability to effectively counter Israeli forces during their month-long conflict in July-August 2006, which is considered the only military defeat Israel has suffered in its 75-year history.
It is thus notable that this underground network is one of many manifestations of the considerable influence that North Korea has had on the Lebanese militia. More than any other fighting force in the world, Hezbollah has shown strong commonalities with the Korean People’s Army in how it has developed its capabilities over the past two decades. Israeli experts referred to Hezbollah’s war effort in 2006 as “a defensive guerrilla force organized along North Korean lines,” highlighting that “all the underground facilities, including arms dumps, food stocks, dispensaries for the wounded, were put in place primarily in 2003–2004 under the supervision of North Korean instructors.” Other intelligence sources indicated that Hezbollah was “believed to be benefiting from assistance provided by North Korean advisers” on the ground.
Research Department director Tal Beeri of the Israeli Alma Research and Education Center, the country’s leading center for the study of Hezbollah-related security challenges, more recently highlighted that the hundreds of kilometers of underground fortifications were at the core of the Lebanese militia’s ability to wage war with Israel. “In our assessment, these polygons mark Hezbollah’s staging centers as part of the ‘defense’ plan against an Israeli invasion of Lebanon. Each local staging center (‘defense’) possesses a network of local underground tunnels. Between all these centers, an infrastructure of regional tunnels was built, interconnected [with] them,” he observed in an interview with the Times of Israel.
With these facilities able to accommodate trucks, they allow Hezbollah to provide security to its mobile ballistic missile launchers much as North Korean forces do. As Beeri stated: “subterranean infrastructure enables a truck to transit to the place where the missile is to be fired. In theory, at the launch site, a platform can be constructed, or a slope leading up from the tunnel. The truck exits the tunnel, fires and goes back down.”
Regarding the North Korean influence on Hezbollah and its role in bolstering the militia’s fighting prowess, and its network of underground fortifications in particular, Beeri elaborated:
Digging tunnels in Lebanon was done from the start with the assistance of North Korea – as far back as the 1980s and especially toward the end of the ‘90s. There is evidence of this. North Korea has historic expertise in the digging of tunnels in mountainous and rocky areas… Eventually, Hezbollah got everything it needed from the Koreans. By 2014, they’d had 25 years of interaction, in the course of which Hezbollah received knowledge and technology to the point where it was able to dig and build the tunnels by itself.
The tunnel and bunker network in the region south of Lebanon’s Litani river alone was by 2006 estimated to have over 600 ammunition and weapons bunkers fortified eight or more meters underground – alongside better fortified command bunkers constructed to a depth of 40 meters using poured concrete. By that time there were at least ten Korean-built tunnel and bunker networks in southern Lebanon – each with dozens of command bunkers, which in turn were each divided into several rooms.
When war broke out that year, Hezbollah’s rocket artillery systems were often deployed from firing pits five meters deep, with foot-thick poured concrete frames reinforced with blast walls and covered with sandbags and thermal blankets, minimizing positions’ heat signatures and making them highly resilient to Israeli air or artillery strikes. North Korean-style tunnels thus served as a force multiplier, which was at the core of Hezbollah’s ability to achieve military success.
This closely mirrored how the Korean People’s Army was itself hoping to counter a U.S.-led assault on a much larger scale in the event of war on the peninsula.
North Korean expertise in tunneling and underground fortifications has its origins in the Korean War, when U.S. forces dropped 635,000 tons of bombs across the peninsula. An estimated 20-30 percent of the northern population died in the war. In the war’s aftermath, in parallel to a major focus on developing a modern air defense capability, key military and industrial sites including entire airfields were built deep underground to prepare for the possibility of a similar air assault.
A recent example of North Korea’s ability to build airbases under mountains was provided in February 2023 when Iranian media released images of the country’s Eagle 44 airbase, likely intended to host newly ordered Russian Su-35 fighters, which is considered highly likely to have been built with extensive North Korean support. Iran’s Fordow uranium enrichment plant is similarly thought to have been built with extensive North Korean assistance and was heavily fortified under a mountain. North Korean knowhow in underground fortifications was previously also exported to China and offered to Vietnam during the Cold War.
Although footage of examples from within North Korea is more scarce, the Pyongyang Metro was notably built from 1965 as the deepest in the world after the United States began deploying and rapidly expanding an arsenal of several hundred nuclear weapons in South Korea, which were largely aimed at the North and peaked at 950 warheads. Three thick metal blast doors at every entrance allow the metro to serve as a shelter in the case of U.S. nuclear strikes. Indeed, this is arguably the Pyongyang Metro’s primary purpose, since the need for underground transportation in the uncrowded city remains limited.
North Korea’s network of tunnels has consistently been a major factor complicating possible planning for military operations against the country. North Korea has the ability to store and manufacture vast arsenals underground, and move them over long distances on underground roads, making it near impossible to ascertain the locations of key weapons and highly challenging to damage them even when they do briefly surface. This has been a major contributor to the country’s security.
When the Obama administration in 2016 seriously considered launching strikes on North Korea, the Pentagon informed the president that options for a limited preventative attack were effectively non-existent as the country’s highly mobile nuclear delivery systems were stored deep underground in facilities which the U.S. military could not locate or neutralize from the air. The Pentagon had thus concluded that not only was it infeasible to seriously set back nuclear and missile development with an attack, as then-President Obama had intended, but also that nothing short of a full-scale ground invasion could disarm North Korea.
The importance of North Korea’s underground fortifications was reflected earlier in Defense Secretary Donald Rumsfeld’s confirmation hearing in January 2001, when he argued against launching a military attack against the country: “They have gone underground across that country in a way that few nations have done… They have underground emplacements of enormous numbers of weapons.” Rumsfeld thus referred to North Korea’s armed forces as “world class tunnellers.”
Underground fortifications are far from invulnerable. Special “bunker buster” assets such as GBU-57 and nuclear B61-11 bombs are able to reach deep underground, while others such as the Taurus KEPD 350 cruise missile can penetrate less well protected positions. However, such assets are highly costly and compromise only small fractions of any country’s arsenals. This makes even the much smaller tunnel network in southern Lebanon effectively impossible to destroy from the air, let alone the underground networks in North Korea.
Underground fortifications are far from the only means by which North Korea has contributed to Hezbollah’s military potency, with the militia’s intelligence and security network built by Korean-trained specialists such as Ibrahim Akil and Mustapha Badreddine. In parallel to this support, North Korean forces have also fought alongside Hezbollah in Syria, such as at the battle of Al Qusair where North Korean artillery advisers were present, combating an insurgency that was strongly and directly supported by Israel, Turkey and other U.S.- aligned regional and extra-regional actors.
North Korea’s ability to construct tremendous networks of underground fortifications particularly in mountainous or rocky terrain has been a major game changer for the balance of power not only on the Korean Peninsula, but also in southern Lebanon. Hezbollah might have been nearly eradicated in 2006, in accordance with Israeli objectives at the time, had it been forced to deploy its assets on the surface. Hezbollah’s utilization of these networks to achieve major unexpected military successes in 2006 ultimately did much to vindicate decades of tremendous investments in underground fortifications by Pyongyang and the pairing of these with an emphasis on artillery and missile assets as a means of providing an asymmetric defense.
With these fortifications continuing to represent a leading constraint on the Israel Defense Forces’ freedom of action, they have also highlighted the magnitude of the challenges the much larger underground network in North Korea would pose to the United States and its allies in the event of a war on the peninsula.