Gen. Qassem Suleimani, a senior Iranian commander and one of the most powerful figures in the Middle East, was killed in an airstrike on the Baghdad International Airport in Iraq at the direction of President Donald Trump, the Pentagon confirmed Thursday. The assassination marks a monumental escalation toward Iran.

“This strike was aimed at deterring future Iranian attack plans,” the Pentagon said in a statement. “The United States will continue to take all necessary action to protect our people and our interests wherever they are around the world.”

Abu Mahdi al-Muhandis, a pro-Iranian militia leader who was a senior figure in Iraq’s government-linked Popular Mobilization Forces, was also killed in the Iraq attack, according to reports from The Associated Press and Reuters.

The incident will have mammoth implications for the Middle East because Suleimani was the central figure in Iran’s significant network of influence across the region. It’s likely to seriously affect the U.S. position there ― with Tehran’s allies already blaming Washington for the death, a greater escalation between U.S. and Iranian forces and their partners appears inevitable. Thousands of U.S. forces are currently within rocket range of Iran’s military and in close proximity to Iran-backed fighters, chiefly in Iraq and Syria, as part of deployments in the ongoing fight against the self-described Islamic State (ISIS). 

The U.S. launched strikes against targets linked to Iran on Friday, officials told Reuters. According to The Washington Post, the Trump administration reportedly began discussing the strike last week after an American contractor died in an attack that U.S. officials blamed on the Iran-backed militia Kataib Hezbollah.

At least five people died in the flare-up, according to The New York Times, including Suleimani and Muhandis.

“The American and Israeli enemy is responsible for killing the mujahideen Abu Mahdi al-Muhandis and Qassem Soleimani,” Ahmed al-Assadi, a spokesman for the Iraqi militia coalition to which Muhandis belonged, told Reuters.

Iranian Foreign Minister Javed Zarif called the airstrike “extremely dangerous” and a “foolish escalation.”

“The US bears responsibility for all consequences of its rogue adventurism,” Zarif tweeted.

Sen. Chuck Schumer, the top Democrat in the Senate, was not given any advance notice of the airstrike, according to an aide.

Trump administration officials did not immediately provide information on their plans to manage the fallout from the strike.

“I worked the Iran account for years at the [White House] under two presidents. I’m honestly terrified right now that we don’t have a functioning national security process to evaluate options and prepare for contingencies,” Kelly Magsamen, a vice president at the Center for American Progress, wrote on Twitter. “God help us.”

The U.S. and Iran both work closely with the Iraqi state and tacitly cooperated in the country for years to combat ISIS. Both have major presences in the country. Experts worry that if their relationship deteriorates further ― and if Baghdad becomes wary of the U.S. because of Iranian pressure or Iraqi anger about American violations of the nation’s sovereignty ― America could face a new national security risk and lose crucial gains in the counterterrorism fight.

Demonstrators connected to Iran besieged the U.S. Embassy in Baghdad earlier this week after Trump ordered strikes on a pro-Iranian militia in Iraq last weekend. Analysts expected some kind of American pushback, but most appeared surprised by how far Trump went. Though hawks like Rep. Adam Kinzinger (R-Ill.) celebrated the news, their messages didn’t extend to commentary on the long-term effects of the killings. 

It’s also unclear what degree of military action Washington will now choose to engage in, and scholars dispute the legal interpretations it will base them on. Suleimani and Muhandis were both members of organizations that the U.S. designates as terrorist groups, but American decision-makers have not in recent years made a habit of targeting their forces or leaders of their rank in this way.

Suleimani’s absence could reshape Mideast politics. Local power brokers saw him as a highly capable operative who could cause serious damage ― including to American interests ― yet managed to largely do so in ways that served his and Iran’s overall strategy. His country’s leadership is likely to feel it must react strongly and loudly, and could do so in a variety of contexts.

“Soleimani was an enemy of the United States. That’s not a question,” Sen. Chris Murphy (D-Conn.) wrote on Twitter. “The question is this - as reports suggest, did America just assassinate, without any congressional authorization, the second most powerful person in Iran, knowingly setting off a potential massive regional war?”

Trump did not issue a public statement on the attacks. Instead, he tweeted a photo of the U.S. flag and did not include any text.

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This article originally appeared on HuffPost.