In April 2017, a lumbering MC-130 with its four whirring propellers flew over a mountainous area in eastern Afghanistan. Just before eight in the evening, the plane dropped a 9,797 kilogram bomb, known as a GBU-43,the largest non-nuclear bomb ever used, on a tunnel network used by Islamic State in Afghanistan.
Thirty-six ISIS members were killed in the massive explosion that followed, according to US estimates. The ISIS tunnel network was more complex than the one that Hezbollah has built in southern Lebanon, but just as the US has had to contend with terrorist tunnels, Israel and all countries facing terrorism are increasingly forced to fight an underground war.
The complexity of caves and tunnels is one of many used by terrorist groups in Afghanistan. ISIS, like many terror groups, have become experts in tunnels. They didn't invent this on their own.
They graduated from what other terror groups have used and used tunnels that have existed in places like Iraq, Syria and Afghanistan for decades. Some of these are bunker complexes that various regimes built, improved upon by terrorists, or they may be terror tunnels built by other groups such as the Taliban and Al-Qaeda.
In Douma in Syria, the Syrian rebels built a massive complex of tunnels. BBC called it "quite a work of engineering." It was excavated from solid clay and stones and was big enough to "drive a vehicle down." One reporter who went down into the tunnels in Douma called it was a "subterranean life."
Hezbollah's tunnels into Israel have now been revealed in a recent video after Israel began operation Northern Shield.
So far, the tunnels under the border have not consisted of such massive complexity and are not equipped with places for vehicles. To understand their origin and the kinds of difficulty in confronting this issue, we must look back at the Second Lebanon War of 2006.
Hezbollah spent decades improving its terror infrastructure in southern Lebanon. After Israel withdrew in 2000 from Lebanon the leaders of Hezbollah planned an extensive network of what were labeled "nature reserves" by Israel, complex tunnels and bunkers designed to conceal the growing arsenal of the group.
They attempted to make them not only difficult to find but also difficult to bomb, according to a 2016 article by the Foundation for Defense of Democracies.
According to the report, they built fortified areas in 200 villages. In an article published by the US Army Combined Arms Center in 2008, the authors looked at Hezbollah's tunnel expertise.
According to this study, which quoted an Iranian Revolutionary Guard Corps officer, Hezbollah had "North Korean advisors [who] had assisted Hezbollah in building tunnel infrastructure." One tunnel was supposedly 25 kilometers long. This extraordinary claim, printed in Asharq Al-Awsat, may not be accurate. One IDF soldier remarked that after the 2006 war, he found a bunker near Maroun al-Ras. It was 25 feet deep, linked several rooms, and had a camera that Hezbollah used to monitor outside movement.
The US army report suggests that Hezbollah – which was born in the 1980s – might have been inspired by the Viet Cong who used tunnels to confront the US military in Vietnam in the 1960s.
The Viet Cong dug massive tunnel systems. One at Cu Chi was 250 kilometers long. Hezbollah might have sought to copy the Vietnamese, but it also wanted to exploit modern technology. Tunnels that were found in 2006 included some with hydraulic steel doors.
Considering Hezbollah's close relationship with Iran and also the Syrian regime it should be expected that Hezbollah's expertise in tunneling has more similarities with the kind of network a state might be able to create, and not just a terrorist organization. This means that tunnels have levels of technology, depth and ability to go through difficult terrain. However, as has been shown in the Syrian civil war context, any group that has even limited resources and devotion, can build impressive tunnels.
Confronting tunnels is a complex task. Militaries and law enforcement agencies, such as those dealing with drug trafficking and smuggling, have to monitor tunnels. In Gaza, the tunnels built under the border with Egypt were used to smuggle people, infrastructure and weapons. Militaries can bomb tunnel networks, like the US did in Afghanistan, but only if they aren't located in civilian areas. ISIS, for instance, festooned civilian areas with tunnels so that its fighters could pass unnoticed under houses and roads. They were able to hold out against a 70-nation Coalition and the Iraqi army in Mosul for 9 months by using these tunnels.
Armies don't like to send men down into tunnels because naturally the enemy has advantage in its own tunnel system and can neutralize a modern army's technological advantage. In 2016, The New Yorker noted that Israel had developed a kind of "underground Iron Dome" to confront tunnels. But Brig.-Gen. (res) Danny Gold, who helped pioneer the above ground Iron Dome and said that "since the Vietnam War it [tunnel threats] hasn't been solved. Between Mexico and the United States it isn't solved. Sometimes it's even harder than finding oil in the ground." An Israeli system, according to this report, cost hundreds of millions of dollars, some of which the US supposed was to "field some four hundred different ideas for the detection and destruction of tunnels."
But for countries fighting tunnels, detection is only one issue. Armies can listen for the tunnel or postulate on where it might be, but don't want any threats or find any surprises when trying to unearth it. This may not be such an easy challenge to confront in an environment with civilians around. Once detected the goal would be to stop the tunnel if it is a threat. But a country might want to monitor what the enemy is doing before interdicting the tunnel. Also a means to dig a counter-tunnel has to be developed and used without alerting the adversary that the counter-tunnel is moving toward the original. Different countries have employed different means. Egypt flooded the tunnels along the border. The most important aspect of confronting tunnels may also be mapping their point of origin to know what threats may be lurking where they begin. Tunnels in warfare have not only been used to hide men and material, but sometimes to store explosives. Israel, by necessity, has become proficient at confronting tunnels. Hezbollah, like other terror groups and like its allied regimes, has also likely increased its skills. The subterranean war will continue to be a layer of the modern battlefield.