Jeffery James, the commander of one of the U.S. ships said Sunday that the message was taken seriously because it came as Iranian vessels swarmed the American fleet.

James and Capt. David Adler of the cruiser USS Port Royal spoke to reporters Sunday at the Bahrain headquarters of the Navy’s Fifth Fleet, which patrols the Persian Gulf.

“This was not a loose bunch of guys,” said Cmdr. Jeffery James of the destroyer USS Hopper. “During this entire time, we were going through our pre-planned responses trying to warn them off before we had to take any lethal action.” he said.