“The president got some additional information that the Iranian national leaders were frustrated or furious with the tactical commander who made the decision to shoot down the American drone,” General Keane said in an interview. Among those who were said to be angry, he said, was Qassim Suleimani, the powerful commander of Iran’s elite Quds Force.

General Keane said it was unclear whether the commander who ordered the downing of the drone was operating within his authority or was a rogue figure. But either way, he said, it impressed upon Mr. Trump that he would be risking a dangerous escalation over what was not intended to be an attack by Iran’s top leaders.