As Allied forces continued their march against Berlin in the West of Europe during World War 2 (1939-1945), the need grew for air defense against low-flying enemy aircraft. The Allied columns emerging from the stocked beach heads of France and Italy lay vulnerable for long stretches of road making them very tempting targets to patrolling German strike aircraft. Additionally, frontline forces required point defense in the same way while they calculated their responses to enemy movements and actions. For the American Army, the M33 Maxson was in inventory to help shore up the requirement. This system came from the W. L. Maxson Corporation and fielded a modest pair of heavy machine guns. However, a better solution followed as the M45 "Quadmount" which - as its name would suggest - fielded no fewer than four 0.50 caliber Browning M2HB heavy machine guns. Despite the M2's rather low rate-of-fire, the coupling of four units would minimize this limitation and provide the voluminous fire required.
Due to its ferocity in combat - particularly against infantry elements - the M45 Maxson was nicknamed the "Krautmower" and the "Meat Chopper".
As designed, the M45 was a complete anti-aircraft defense system combining guns, turret and mounting. The operator (gun-layer) sat in a tub-type assembly straddled along either side by a pair of 0.50 caliber Browning heavy machine guns. The machine guns were each fed by way of a 200-round, 90-pound magazine cassette affixed at each receiver feed. Typically, two ammunition handlers (loaders) were assigned to a M45 unit for streamlined function. The turret portion was designed with electrically-powered assist which allowed for traversal (a full 360-degrees) and elevation (spanning from -10 to +90 degrees). As the M2 Brownings were air-cooled weapons by their inherent design, the operator would need to take special care to combat barrel overheating. As such, typical operation in-the-field involved the operator firing the upper or lower gun pairs in turns, allowing one pair to cool while the other engaged.
The M45's special mounting component allowed the entire system to be mounted onto a two- or four-wheeled carriage (M20 or M17 trailer respectively) for transporting behind a designated mover vehicle. Additionally, the M45 could be affixed to the flatbed section of a military transport truck of mechanized halftrack vehicle. When mounted on an M3 Halftrack, the complete vehicle was designated as the "M16 Gun Motor Carriage" (GMC). Its attachment to the M17 trailer produced the "M51 Multiple Machine Gun Carriage" (MMGC) designation and, when mounted atop the M20 trailer, the system became the "M55 Machine Gun Trailer Mount" (MGTM).
In practice, the M45 Quadmount gave exceptional service for its given short-ranged, air defense role. As Allied air supremacy grew and forces expanded throughout France and beyond, there proved a greater need for protection against marauding enemy strike aircraft. While the M45 was limited in effective range to an extent by its use of machine guns, its voluminous approach allowed it to fill the immediate skies with hot lead at a moment's notice. Beyond its obvious value as an anti-aircraft measure, the M45 was found to be a highly lethal anti-infantry weapon when bringing its guns to bear on unprotected targets and even soft-skinned vehicles - making the M45 something of a multirole solution.
In one notable action regarding M45s during March 1945, nearly 250 German aircraft attempted an assault at Oppenheim near the Rhine River in attempt to destroy a strategic crossing. Over a quarter of the attackers were felled, primarily due to the presence of the M45 in the American force. The bridge was saved from destruction and later crossed by Patton's 3rd Army.
In the post-World War 2 years, the M45 saw extended service. One particular evolution was handled by the new Israeli Army which mated a pair of 20mm Hispano-Suiza HS.404 series autocannons to the turret component of the M45 Maxson. This produced the TCM-20 which gave good service for several decades before replaced by a more modern component in the American M163 "Vulcan" Air Defense System (ADS). This vehicle coupled the Vulcan Gatling-style minigun weapon with the tracked chassis of the M113 Armored Personnel Carrier (APC).