The U.S. Navy has continued to expand its new force of port security units. Two years ago, the navy organized three Mobile Security Detachments. Each has 80 sailors, three 25 foot boats, plus lots of weapons, sensors and communications gear. There are now nine of these Mobile Security Detachments, with another three being organized. Originally intended for protecting American ports, detachments have gone on to train self-defense teams for American warships, and, on six month rotations, guarded port facilities in Iraq. The navy has never had a Military Police force like the army and air force do, but the Mobile Security Detachments are turning into that. Previously, the navy had a job category, Master at Arms, which specialized in security. But now, there are thousands more sailors trained as Master at Arms, or serving in Mobile Security Detachments.