Some lawmakers have called Trump's strikes on Iran "unconstitutional" - so did he have the authority to order them?

In a sense, then, this felt like a repeat of 2020, when Iran fired missiles at an American base after Mr Trump ordered the assassination of Qassem Suleimani, an Iranian general. The target back then was Ain al-Asad, a base in western Iraq. No American troops were killed thanks to ample warning, though scores were hurt, many with concussions.

Few people inside the administration knew the president was moving forward with plans for the attack, even late last week.