But it was an unusual admission from Mr. Gerecht, who has regularly criticized the president, dating to the 2016 campaign, when he was among the dozens of Republican foreign policy insiders who added their names to a letter denouncing Mr. Trump as unfit to lead the nation and collectively came to be known as Never Trumpers.

“I don’t think it changes the larger analysis,” Mr. Gerecht cautioned, arguing that Mr. Trump remained a major disappointment on foreign policy issues like his criticism of NATO allies and his lack of support for Western democratic values throughout the Middle East. But, Mr. Gerecht added, “on Iran, which is the most important one in the Middle East, he is getting that one more or less right.”

It was clear on Monday that Mr. Gerecht spoke for many of his ideological comrades, who generally believe that military force can be a positive tool and not always a dreaded last resort, and that Iran in particular is likely to back down when confronted with strength. Many of them are collectively known as neoconservatives, or neocons, even if not all of them accept the label.

Many of those hawks have long applauded Mr. Trump’s sanctions-based “maximum pressure” campaign against Iran, but they had come to doubt the president’s willingness to use military force and were delighted to see him take action against someone responsible for consolidating Iranian influence at the expense of many American lives.

Other frequent Trump critics who cheered the strike against General Suleimani include Representative Liz Cheney of Wyoming, a frequent critic of Mr. Trump’s foreign policy who posted on Twitter shortly after the Iranian commander’s death that Mr. Trump was “was right to order decisive action to kill” him.