Army - M109 155mm Sp - Ft Fill Ok W Arty Br T Shirt - ClassicThe M109 is an American 155 mm turreted self propelled howitzer, first introduced in the early 1960s to replace the M44. It has been upgraded a number of times, most recently to the M109A7. The M109 family is the most common Western indirect fire support weapon of maneuver brigades of armored and mechanized infantry divisions.