The Japan Maritime Self-Defense Force ( Kaij Jieitai), or JMSDF, is the maritime branch of the Japan Self-Defense Forces, tasked with the naval defense of Japan. It was formed following the dissolution of the Imperial Japanese Navy after World War II. It has a large fleet with significant blue-water operating capabilities. The force is based strictly on defensive armament. Its main tasks are to maintain control of the nation's sea lanes and to patrol territorial waters. It has also stepped up its participation in UN-led peacekeeping operations (PKOs) and Maritime Interdiction Operations (MIOs). The JMSDF has an official strength of 46,000 personnel (currently around 45,800 personnel), operating 119 major warships, including 20 submarines, 53 destroyers and frigates, 29 mine warfare ships, 9 patrol craft and 9 amphibious ships (total displacement of approx. 432,000 tons). It also has 179 fixed-wing aircraft and 135 helicopters. Most of these aircraft are used in antisubmarine andmine warfare operations. The ship prefix for JMSDF ships is JDS (Japanese Defense Ship) for all ships commissioned before 2008.