“These strikes were defensive, proportional, and in direct response to the threat posed by Iranian-backed Shia militia groups (SMG) who continue to attack bases hosting OIR coalition forces,” the Pentagon added.

Kata’ib Hizbollah has been behind nearly two dozen rocket attacks on U.S. and coalition troops in Iraq. The list below shows the attacks perpetrated by the group, in the past 13 months, against bases where American and coalition troops are stationed. 

After an attack in late December where an American contractor was killed, the U.S. targeted the militia with heavy airstrikes. That led to the Iranian-led militia attacking and attempting to storm the U.S. Embassy. 

The U.S. retaliated further by taking out the Iranian commander of the Quds Forces, MG Qassam Soleimani, the man behind the attacks with a drone strike. Iran then launched dozens of missiles at another U.S. base. No troops were killed but about 100 suffered concussions from the strikes.  

On this latest attack, Defense Secretary Mark Esper said that he acted after President Trump gave him the authority to take whatever action he deemed necessary. 

“Yesterday’s attack by Iranian backed Shia militia groups consisted of multiple indirect fires that originated from a stationary platform and was clearly targeting coalition and partner forces on Camp Taji,” Esper said.

“The United States will not tolerate attacks against our people, our interests, or our allies. As we have demonstrated in recent months, we will take any action necessary to protect our forces in Iraq and the region. We’re going to take this one step at a time, but we’ve got to hold the perpetrators accountable. You don’t get to shoot at our bases and kill and wound Americans and get away with it.”

Chairman of the Joint Chiefs, General Mark Milley, said on Thursday that the truck that fired the 107mm Katyusha rockets was secured by Iraqi Security Forces and forensics gathered from that vehicle helped identify who was responsible for the attack.

“We have pretty good confidence who did this. We were able to capture the truck, it was a modified truck with tubes, rocket tubes on the back, the Iraqi security forces did a good job in helping secure that truck. We have good indications based on forensics where it was fired from, who did the firing and so on and so forth,” Milley said.

U.K. Defense Minister Ben Wallace released a statement later on Thursday expressing the support for the American decision to strike back.

“The coalition stands should to shoulder in Iraq,” he said. “Our forces work together to help the country resist the malign activity of terrorists. When we and others are attacked, we reserve the right to defend ourselves.”

“We support the right of the United States to defend themselves, as they have done tonight,” he added. “We reiterate that those who seek to harm our armed forces can expect to receive a strong response.”

While the coalition and the militias are both there ostensibly to fight against ISIS, the Iranian-led militias have consistently attacked bases where Americans are stationed. They’ve threatened to continue attacking American troops until the United States completely withdraws from Iraq.

The Iraqi government summoned both American and British diplomats to protest the “violation of sovereignty and targeted aggression” against their armed forces. “The foreign minister held an emergency meeting in which the ministry’s undersecretaries, advisors, and official spokesman discussed the measures regarding the recent American aggression.”

The foreign minister, however, made no mention of the Iranian-proxy militia attacking the same sovereignty 20 times in the past year.