The killing — which the Pentagon said was justified by a need to prevent future Iranian attacks — is a dramatic escalation of President Trump’s “maximum pressure” campaign against Iran, which began with economic sanctions.

Analysts and officials predicted retaliatory attacks from Iran and its proxies, and critics of Mr. Trump’s Iran policy called his strike a reckless escalation with consequences that could ripple violently throughout the Middle East. Presidents George W. Bush and Barack Obama had both rejected killing General Suleimani, fearing it would lead to war.

Details: The drone strike hit two cars carrying General Suleimani, who had arrived from Syria, and several officials with Iranian-backed militias as they were leaving the Baghdad airport. The strike came days after American forces bombed three outposts of an Iranian-supported militia in Iraq and Syria, in retaliation for an attack that killed an American contractor last Friday.

Background: American officials consider General Suleimani, the commander of the Revolutionary Guards’ elite Quds Force, responsible for the deaths of hundreds of American soldiers during the Iraq War and for hostile Iranian activities throughout the Middle East.

Justification: After the strike, the Pentagon said that General Suleimani had “orchestrated attacks on coalition bases in Iraq over the last several months,” including one that killed the American contractor. It also said he had “approved the attacks” this week on the U.S. Embassy compound in Baghdad, in which protesters had broken into a secure area and set fires.