Previously Bolton and Pompeo had urged Trump to assisanate Soleimani in retaliation for Iran shooting down an American drone. Trump refused at the time, claiming it would only be an option if Iran killed an American.
Kataib Hezbollah has been attacking bases housing Americans. Its widely believed they take direction from Quds Force and have gradually been upgrading their weaponry, firing 122mm rockets. Their largest attack in Dec 22nd killed an American contractor.
Trump authorized the killing after Iranian back protesters stormed the American embassy. That was the retaliation option that involved the fewest possible casualties.
After Iran shot down a U.S. drone in June, John Bolton, Trump's national security adviser at the time, urged Trump to retaliate by signing off on an operation to kill Soleimani, officials said. Secretary of State Mike Pompeo also wanted Trump to authorize the assassination, officials said.
But Trump rejected the idea, saying he'd take that step only if Iran crossed his red line: killing an American. The president's message was "that's only on the table if they hit Americans,"
The administration of President George W. Bush designated the Quds Force a foreign terrorist organization in 2007. Four years later, the Obama administration announced new sanctions on Soleimani and three other senior Quds Force officials in connection with an alleged plot to assassinate the Saudi ambassador to the United States.
But in April, Bolton helped prod Trump to designate the entire Islamic Revolutionary Guard Corps a foreign terrorist organization.
Iran has launched more than a dozen separate rocket attacks on bases housing Americans since October. The U.S. military blamed Kataib Hezbollah, an Iraqi militia that is part of the Popular Mobilization Forces but is backed by Iran. U.S. military and intelligence officials say the group takes direction from Iran, specifically the Quds Force.
Most attacks in October and November used 107mm rockets, which have a shorter range and less explosive power. But an attack on Ain al Asad air base in Anbar Province on Dec. 3 included 122mm rockets, with more firepower and the ability to be fired from a greater distance. They are generally launched from more sophisticated improvised rail systems, leading the U.S. military to believe the attackers were receiving new equipment and training from Iran.