WarSclerotic

In April 2017, a lumbering American MC-130 prop plane flew over a mountainous area in eastern Afghanistan. Just before 8 p.m., the plane dropped a 9,797 kg. bomb, known as a GBU-43, the largest non-nuclear explosive ever used, on a tunnel network used by Islamic State. Thirty-six ISIS members were killed in the massive explosion that followed, according to US estimates. That 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 complex of caves and tunnels is one of many in Afghanistan used by terrorist groups. ISIS, like many terrorist groups, has become expert in tunneling. ISIS didn’t invent this on its own. The group expanded on technology that other terrorist groups have used. ISIS also used tunnels that have existed in places like Iraq, Syria and Afghanistan for decades. Some of these are bunker complexes that various regimes built and were improved upon by the terrorists, or they may be terrorism tunnels built by groups such as the Taliban and Al-Qaeda.

In Douma, Syrian rebels built a complex of tunnels which the BBC termed “quite a work of engineering.” Excavated through solid clay and stones, it was big enough to “drive a vehicle down.” It was a “subterranean life,” said the reporter said who descended into the Douma tunnels.

Four of Hezbollah’s cross-border tunnels into Israel have now been exposed since Israel began Operation Northern Shield. None of these tunnels were large enough for vehicles. To understand their origin and the kinds of difficulty in confronting them, we need to look back at the 2006 Lebanon war. Hezbollah spent decades improving its terrorist infrastructure in southern Lebanon. After Israel withdrew in 2000 from southern Lebanon, Hezbollah’s leaders planned an extensive network of what were labeled “nature reserves” by Israel, complexes of tunnels and bunkers designed to conceal the group’s growing arsenal. Hezbollah 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 by David Daoud, it built fortified areas in 200 villages. In an article called ‘We were caught unprepared’ 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 advisers [who] had assisted Hezbollah in building tunnel infrastructure.” One tunnel was supposedly 25 km. long. This extraordinary claim, printed in the London-based daily Al-Sharq al-Awsat, may be inaccurate. The actual reports of the tunnel system by one IDF soldier after the 2006 war, quoted in a book called Back to Basics, remarked that he found a bunker near Maroun al-Ras. It was 8 meters deep and linked several rooms. It had a camera that Hezbollah used to monitor movement outside.

The US army report suggests that Hezbollah, which was founded in the 1980s, may 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 km. in extent. 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 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 the 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 sophisticated tunnels.

Confronting tunnels is a complex task. Militaries and law enforcement agencies which deal with drug trafficking and smuggling both have to monitor tunnels. For instance, 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 in Mosul for 9 months using these tunnels, against a 70-nation Coalition and the Iraqi army.

Armies don’t like to send men down into tunnels because naturally the enemy has the advantage in its own tunnel system allowing it to neutralize a modern army’s technological superiority. The New Yorker in 2016 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, told the New Yorker 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 was supplied by the US, to “field some 400 different ideas for the detection and destruction of tunnels.”

But for countries fighting tunnels, detection is only one issue. You can listen for the tunnel or postulate on where it might be, but you don’t want any threats coming from it or surprises when trying to unearth it. This may not be such an easy challenge to confront in an environment with containing civilians and homes. 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 Gaza 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.