COLUMBUS (WCMH) — The U.S. says it is sending more troops to the Middle East and Iran has vowed “harsh retaliation” for a U.S. airstrike near Baghdad’s airport that killed its top general.

Gen. Qassem Soleimani was the architect of Iran’s interventions across the Middle East and the head of Iran’s elite Quds Force. His killing marks a major escalation in the standoff between Washington and Iran.

Iran’s supreme leader warned that a “harsh retaliation is waiting” for the U.S.

The killing and Iran’s response could ignite a region-wide conflict.

The U.S. ordered its citizens to leave Iraq, closed the embassy in Baghdad, and ordered 3,000 additional Army troops from the 82nd Airborne Division to Kuwait.

President Donald Trump said the killing of Soleimani was not undertaken in an effort to begin a conflict with Iran.

Speaking to reporters in Florida for the first time since the drone strike on Soleimani, Trump said, “We took action last night to stop a war. We did not take action to start a war.”

Trump also said he does not seek regime change in Iran, but the nation’s use of “proxy fighters to destabilize its neighbors must end and it must end now.”

Trump adds that targets of possible retaliation have been identified “and I am ready and prepared to take whatever action is necessary.”

The unprecedented killing of Iran’s top general has sent shockwaves across the Middle East. Iran and its allied forces have vast arsenals and are within striking distance of U.S. troops deployed in Syria, Iraq and the Gulf.

But they may be wary of launching a retaliatory attack that could ignite a major conflict.

The targeted attack itself could give them pause by signaling that the mercurial Trump is willing to wield U.S. military power in dramatic and unforeseen ways.

Peter Mansoor, a professor of military history at The Ohio State University, said Soleimani had been directing proxy militia attacks on U.S. interests for a long time.

“Something like this was inevitable,” Mansoor said. “The Trump administration had to respond to these provocations. But to do so by killing one of the top Iranian officials is a real escalation of tensions in the regions for sure.”

Mansoor did two tours of duty during the Iraq War and served as the executive assistant to Commanding General David Petraeus.

He said Soleimani was directly responsible for killing 600 U.S. servicemen during the Iraq War and wounding 20,000 others.

“The first thing I thought when I heard about this strike that killed him was justice has been served because certainly, he deserved what was coming to him,” Mansoor said.

Mansoor said Iran’s response to Soleimani’s death will be calculated.

“I think the most likely response will be some sort of asymmetric response,” he said. “They’ll use their proxy forces around the Middle East to attack U.S. interests, maybe oil tankers in the gulf, maybe U.S. bases directly in Iraq.”

“I think the real wildcard here is the Trump administration because it’s the one that is really not acting with prudence,” Mansoor added. “It has taken a major step, some people might say that it is justified, you could certainly make the case that it was justified, but there’s no doubt that it was a major escalation in the conflict.”