The M109 was introduced in the early 1960s to provide indirect fire support to armoured and mechanised infantry divisions. It has a crew of six. The M109A6 is armed with a 155mm M284 cannon in a M182A1 gun mount with stowage increased from 36 to 39 rounds.The M109A6 also has an inertial navigation system which improves accuracy of fire allowing it to halt and fire within 30 seconds with the same accuracy as previous variants when emplaced. This allows the M109A6 to operate in smaller numbers and