The M198 howitzer is similar to a large cannon in that it fires a shell towards the target. The M198 howitzer is towed behind a 5 ton truck and fires 155 mm shells. The howitzer can also be transported by C130 aircraft, CH47 Chinook helicopter and dropped by parachute. The M198 is used to provide support fire for Stryker Brigade Combat Teams and Airborne and Air Assault forces. It first entered Army service in 1978 and over 1600 units have been produced. The Marines have 541 of the M198 howitzers in service.