As of this month, the U.S. military had about 40,000 service members in the Middle East, according to a U.S. official.

Iran launched retaliation against the United States on Monday, firing short- and medium-range missiles targeting the U.S. Al Udeid Air Base in Qatar.

About 10,000 troops are stationed at the base, which serves as the regional headquarters for the U.S. Central Command.