The US carried out a round of strikes in Yemen against the Iran-backed Houthis on Wednesday evening, according to Defense Secretary Lloyd Austin, targeting five underground weapons storage facilities using B-2 stealth bombers.

The facilities housed advanced conventional weapons used to target military and civilian vessels in the Red Sea and the Gulf of Aden, three US defense officials told CNN following the attack.

“This was a unique demonstration of the United States’ ability to target facilities that our adversaries seek to keep out of reach, no matter how deeply buried underground, hardened, or fortified,” Austin said in a statement. “The employment of US Air Force B-2 Spirit long-range stealth bombers demonstrates U.S. global strike capabilities to take action against these targets when necessary, anytime, anywhere.”