A sprawling air base in western Iraq that hosted President Trump during his first visit to a combat zone as commander in chief was one of two military installations where American troops are stationed that came under ballistic missile attack by Iran early Wednesday.

Al Asad Air Base, along with an air base near Erbil in northern Iraq, were targeted in retaliation for a drone strike by the United States on Friday that killed Maj. Gen. Qassim Suleimani, a top Iranian commander who Mr. Trump had maintained was planning “a very big attack and a very bad attack for us.”

The fusillade also came one day after Mr. Trump threatened to attack cultural sites in Iran in response to any reprisals for General Suleimani’s killing. Mr. Trump backed away from the threat earlier Tuesday after being told it would be illegal.

Here’s what we know about the bases and the scale of the attack on Wednesday:

Were there any casualties?

The Pentagon announced that more than a dozen ballistic missiles had been fired at the two bases but said it was still assessing the damage. The editor in chief of Mashregh, the main news website for Iran’s Revolutionary Guards, said more than 30 ballistic missiles had been fired at the American base at Asad.