U.S. Military Blasts Islamic State’s Tunnels in Mosul
But getting at underground networks from the air is difficult
by JOSEPH TREVITHICK
On Oct. 17, 2016, Iraqi troops and Kurdish Peshmerga fighters — backed by American and other foreign forces — began to liberate Mosul and its surrounding environs from Islamic State. The offensive quickly uncovered extensive terrorist tunnels in the city.
The Pentagon responded by blasting the underground network for the sky.
“Many of you have seen and noted the enemy’s developed extensive tunneling networks in some of the areas that they use for tactical movement and to hide weapons,” U.S. Air Force Col. John Dorrian, a Pentagon spokesman, told reporters on Oct. 28, 2016.
In total, American strikes destroyed “46 of those tunnels since the liberation battle for Mosul started on October 17th, reducing the threat from a favored enemy tactic.”
However, despite decades of experience, destroying below-ground linkages from the air is still difficult, especially in areas full of innocent civilians. According to the U.S. Air Force, American planes didn’t drop any bunker busting bombs during these missions.
“The BLU-118, BLU-121 or BLU-122 warheads or the GBU-57 Massive Ordnance Penetrator have not been used in the Liberation of Mosul campaign,” Kiley Dougherty, the head of media operations for U.S. Air Force’s Central Command told War Is Boring by email. “ In fact, these weapons have not been used at all in support of Operation Inherent Resolve.”
Inherent Resolve is the Pentagon’s nickname for the campaign against Islamic State in Iraq and Syria.
The Mosul operation is not the Pentagon’s first experience with tunnels. During the Vietnam War, the Viet Cong insurgents famously dug wide-ranging subterranean mazes throughout South Vietnam.
In the 1970s, North Korea dug at least four large tunnels under the Demilitarized Zone to sneak spies and commandos into the South. The top American command on the peninsula created a “tunnel neutralization team” to assess and seal the passages.
Underground bunkers and cave complexes were features in the first Gulf War in 1991, the intervention in Afghanistan in 2001 and the invasion of Iraq in 2003. The Pentagon has taken note of Egyptian and Israeli efforts to stop Palestinian and other militants from digging under their borders.
In December 2001, the American commandos famously tried to flush out Osama Bin Laden and his cohorts from the Tora Bora caves near the Afghanistan-Pakistan border. Massive B-52 bombers pounded the mountains, but could only keep the terrorists hunkered down.
“Entire lines of defense were immolated by cascades of precisely directed 2,000-lb. bombs,” U.S. Army historians wrote in 2005. “But the depths of the caves and extremes of relief limited their effectiveness considerably.”
Air Force MC-130 special operations transports dropped 15,000 pound “Daisy Cutter” bombs, but couldn’t uproot the militants. The Al Qaeda leader eventually slipped across the border to settle near the Pakistani city of Abbottabad.
Within two years, the Pentagon had flown similar missions in Iraq. Despite the bombardment, on Dec. 13, 2003, a team of regular and elite U.S. troops found long-time Iraqi dictator Saddam Hussein very much alive in a makeshift bunker outside the city of Tikrit.
By November 2015, tunnels again appeared as a factor in the fight against Islamic State. Faced with deadly American air strikes, the terrorists had literally gone to ground.
“In November 2015, when Kurdish forces entered Sinjar, Iraq, … they found that ISIL had adapted to air attacks by building a network of tunnels that connected houses,” U.S. Army analysts explained in a February 2016 report, using a common acronym for Islamic State.
“The sandbagged tunnels, about the height of a person, contained ammunition, prescription drugs, blankets, electrical wires leading to fans and lights, and other supplies.”
War Is Boring obtained this and other Army reviews of enemy tactics through the Freedom of Information Act.
But by the time the terrorist tunnels became an issue in Iraq and Syria, the U.S. Air Force had replaced the Vietnam-era Daisy Cutters. Instead, American crews had access to a number of newer specialized bombs.
Shortly after the Tora Bora debacle, American fliers received the first BLU-118s. Pentagon weaponeers cooked up the 2,000 pound thermobaric bombs specifically to blow up caves and tunnels.
Thermobaric warheads create massive, fireball-like explosions. If you can get one into a bunker or other confined space, the blast will bounce off the walls for an even more devastating effect.
In 2005, the Pentagon bought improved BLU-121s with a new delay fuze. This meant the bomb could bury itself deeper inside a tunnel before going off, causing maximum damage. Crews can fit both weapons with laser guidance kits for precise attacks.
And then there are bunker-busters such as the BLU-122 and GBU-57. These bombs have specialized features to break through reinforced sites, deep underground. Only the B-52 and B-2 bombers can carry the 30,000 pound Massive Ordnance Penetrator.
All of these weapons are great for attacking remote caves or isolated, underground military bases. They’re not necessarily good for attacking small tunnels in urban areas.
Even out in the open, fliers generally need powerful sensors or help from troops on the ground just to spot subterranean sites from the air. Though laser and GPS-guided bombs can strike within feet of a specific target, tunnel entrances might not be much larger than a person’s shoulders.
On top of that, in a densely packed city, any errant bombs have a greater chance of hitting unintended targets. A tunnel network under a house or apartment block presents a particularly problematic situation.
Add a thermobaric warhead to the mix and the results could be even more disastrous. There are reports Islamic State turned to human shields to ward off air strikes and Baghdad’s own thermobaric rocket launchers and artillery.
“We have seen many instances in the past where Daesh have used human shields in order to try and facilitate their escape,” Dorrian noted in his press conference. “Right now they’re using human shields to make the Iraqi Security Forces’ advance more difficult.”
The Pentagon would have run into similar hurdles when hitting the terror group’s tunnels in Mosul. By using conventional bombs, American crews might have had a harder time hitting the mark, but could better avoid unnecessary collateral damage. At the same time, this dynamic no doubt serves to reinforce the value of tunnel networks to the Islamic State.
And any assault on the group’s de facto Syrian capital in Raqqa will likely turn up more tunnels.
“Over time, adversaries of the U.S. and its allies have repeatedly shown that they are extremely adept at their use of this type of environment,” U.S. Army experts declared in a review of Hezbollah’s use of tunnels during Israel’s incursion into Lebanon in 2006.
“[This] consequently presents a situation in which, despite the U.S.’s technological superiorities, a threat could potentially gain an advantage over the U.S. and achieve victory.”
Thankfully, so far, Islamic State’s tunnels have only delayed Baghdad’s troops and their American partners.