Cellphone video shows what was left of a desolate outpost on the Syrian side of the border with Iraq after U.S. airstrikes on Thursday. Two F-15 Eagles, completely destroying nine buildings and damaging two. Initial reports said one person was killed and three injured.
"I recognize the significance of this operation, that it's the first of its kind under the new administration," said Pentagon spokesman John Kirby.
Kirby said Iranian-backed militias used the border post to smuggle weapons into Iraq.
"These structures, again, we had information that gave us confidence these structures, this site, this compound – because all the buildings were all on one compound - were being used by these groups to facilitate the movement of resources, material, weaponry into Iraq to conduct the attacks," Kirby said.
Two weeks ago, U.S. officials say, Iranian-made rockets were fired at a base in Iraq where American troops are stationed. Thursday night's strike was a message to Iran.
"That is an unambiguous clear message to anyone in the region about what the stakes are if you're going to continue to conduct attacks on our people," Kirby said.
Defense officials say the strike was intended as a one-and-done, but that will depend on how Iran and its allies react.