The light version, the M108 Howitzer, was phased out during the Vietnam War, but many were rebuilt as M109s. program to adopt a common chassis for its self-propelled artillery units. The M109 was the medium variant of a U.S. for the foreseeable future until the new M1299 will enter service. Crusader and Non-Line-of-Sight Cannon, the M109A6 ('Paladin') will remain the principal self-propelled howitzer for the U.S. (see variants below) and by Switzerland (KAWEST). Upgrades to the M109 were introduced by the U.S. Several European armed forces have or are currently replacing older M109s with the German PzH 2000. The British Army replaced its M109s with the AS-90. The chief or gunner aims the cannon left or right (deflection) and up and down (quadrant). The M109 has a crew of four: the section chief/commander, the driver, the gunner, and the ammunition handler/loader. The M109 family is the most common Western indirect-fire support weapon of maneuver brigades of armored and mechanized infantry divisions. It has been upgraded a number of times, most recently to the M109A7. The M109 is an American 155 mm turreted self-propelled howitzer, first introduced in the early 1960s to replace the M44.
