A deadly modern upgrade to an ancient tactic is emerging as a potent new weapon in Syria, where terror group ISIS has used them to blow up several buildings, it emerged this week. The simple yet effective technique was also used by the group to take the Iraqi city of Ramadi, according to Pentagon officials.
It is a simple enough concept: Dig a tunnel under your target, plant explosives, and press the detonator.
According to the Pentagon organization that studies improvised explosive devices, JIEDDO, at least 45 such devices have been used in the past two years in Iraq and Syria. While most have been used in Syria, U.S. officials say ISIS is building “a network of bunkers, trenches and tunnels” inside Iraq.
“This below the surface attack is particularly destructive to buildings and is appearing increasingly in Afghanistan, Iraq and Syria,” according to a recent JIEDDO briefing.
While tunnels are common in war zones, such as as Vietnam, they continue to be used in modern times, most notably by Hezbollah and Hamas in Gaza. Yet those tunnels have mostly been used for transportation. In Vietnam they served as underground highways and places to live, while in Gaza they are generally used to smuggle weapons and launch attacks against Israel.
ISIS, however, is using tunnel bombs against military checkpoints, buildings and other fortified facilities. It takes less than 30 days to dig a short tunnel, while ones that reach a mile long may take up to nine months, according to JIEDDO.
“The use of tunnels for IEDs and other purposes will continue to provide a low risk strategic advantage to extremist organizations and therefore requires continued development efforts and fielding of effective mitigation techniques,” the JIEDDO report said.
In modern war video footage of buildings collapsing, with massive plumes of smoke and debris flying hundreds of feet into the air, are almost as valuable as destroying the target. ISIS frequently posts such dramatic videos to social media, where they generate significant buzz.
“As part of an information operations campaign, these attacks are documented and widely proliferated via social media which increases the likelihood of migration to other conflict areas or adoption by other extremist organizations on a worldwide basis,” JIEDDO says, illustrating that viral videos can lead to the viral spread of terror tactics.
In Syria, rebels have dug tunnels with hand tools to avoid detection. Their targets have been mainly government forces in small attacks.
In Iraq, ISIS has become a heavy user of tunnel bombs, notably to devastating effect in their assault on Ramadi.
A March 11th tunnel bomb under an Iraqi army headquarters killed 22 people. According to the JIEDDO briefing on the matter the blast consumed an estimated seven tons of explosives. The tunnel was 800 feet long and took two months to dig.
But ISIS isn't just using tunnels for explosives. They're also using them to stealthily move weapons away from the prying eyes of U.S. drones and fighter jets. They have also likely begun using Saddam Hussein's legendary network of tunnels, which stretched over 60 miles.
Pentagon planners are now looking to the oil and gas industry for help on ways to detect tunnels. The industry uses seismology to survey the ground and understand the composition of material below the surface. Defense planners are studying which approaches they can roll out to pilots in the region to help them quickly and effectively locate ISIS tunnels.
Yet there's no certain solution to the problem. Tunnels under city centers will always be difficult to find and tunnels under open areas don't generally exist.
What is certain is that ISIS will continue to use the tactic, recognizing that it makes life difficult for American forces and also makes for a devastating weapon of war.