The targeted killing of Maj. Gen. Qassim Suleimani and four others in a precision strike by an MQ-9 Reaper drone at Baghdad International Airport was an impressive display of American military prowess. And it liquidated a destabilizing figure: The general was the commander of the Quds Force, which is responsible for Iran’s covert and extraterritorial military operations. In the scheme of things, he had it coming. Yet killing him made little strategic sense for the United States. In some ways, the most significant thing about his death is what it shows about the breakdown of American foreign policymaking.

President Trump ordered the strike directly, prompted by the death of an American contractor on Dec. 27 in a rocket attack by Kataib Hezbollah, an Iranian-sponsored Iraqi Shia militia. Mr. Trump did not bother to consult congressional leaders. As with his other displays of martial fiat, his immediate impulse was probably to shock the liberal domestic audience, vicariously make himself feel tough, and assert raw executive power by going around the normal channels of decision making.

Presidents George W. Bush and Barack Obama had considered taking out General Suleimani but rejected it — not for lack of nerve, but for fear of undue escalation and an unnecessary war with Iran. The fundamental facts on the ground have not changed, and in the kind of robust interagency, national security decision-making process that the National Security Council staff is supposed to supervise, such concerns would have been systematically raised, dissected and discussed, and a consensus reached to inform presidential action. No such process seems to have occurred here.

The Pentagon has claimed, facilely, that General Suleimani was hit because the Revolutionary Guard was planning attacks on American targets in the region. But in a proper interagency review, the intelligence community could have pointed out that “decapitation” is a patently unreliable means of pre-emption — particularly when the organization in question is the Revolutionary Guard, an integral part of a well-honed security state with considerable depth of command talent.