M15 Halftrack

The M15 Halftrack, officially designated M15 Combination Gun Motor Carriage, was a World War II United States Army self-propelled anti-aircraft gun on a half-track chassis. It was equipped with one automatic 37 millimeter (1.5 in) gun and two water-cooled 0.5 in (12.7 mm) M2 Browning heavy machine guns in a coaxial mount controlled by a M6 sighting system. It was produced by the White Motor Company between July 1942 and February 1944, and served alongside the M16 Multiple Gun Motor Carriage.

It evolved from the T28 project, initially as the T28E1 Combination Gun Motor Carriage (CGMC). It was accepted into service in 1943 as the M15, equipping US Army armored units during the latter stages of World War II. The 37 mm gun was often used as an infantry support weapon. The M15A1 was an improved variant with air-cooled machine guns mounted below the 37 mm gun. The M15 "Special" was based on the M15 but produced to fulfill the same role by mounting a Bofors 40 mm gun.

During World War II, the vehicle served the U.S. Army throughout the Mediterranean, European, and Pacific Theaters of Operations. During the Korean War, the M15 served alongside the M16 providing support to the infantry.

Design
The M15 was based on the M3 Halftrack chassis – a vehicle built from commercial components to maximize production. The M15 was 20 ft 3 in long, 7 ft 4 in wide, and 7 ft 10 in high, with a wheelbase of 135.5 in. The suspension for the wheels was a leaf spring, while the track bogies had vertical volute springs. The M15 had a fuel capacity of 60 US gallons}, which produced a range of 150 mi, and was powered by a White 160AX, 128 hp, 386 in3,  6-cylinder petrol engine with a compression ratio of 6.3:1, which produced a maximum road speed of 41.9 mph. It had a power-to-weight ratio of 15.8 hp per ton. Armament consisted of a fully automatic 37 mm Gun M1 and two 0.50 cal M2 Browning machine guns mounted above the 37 mm gun. With up to 12 mm of armor it weighed 9.45 tons and had a crew of 7.

Development


The M15 design developed from the T1A2 Multiple Gun Motor Carriage (MGMC) project, which was based on the M2 Half Track Car. With the addition of a 37 mm gun, this design became the T28. The T28 project was canceled in 1942 by the United States Army Coast Artillery Corps.

T28E1
A United States Army Armored Force requirement for a mobile anti-aircraft gun to support the coming North African campaign resulted in the T28 project being revived soon after its cancellation. The new vehicles used an M3 Halftrack chassis, and were designated as the T28E1 CGMC.

A total of 80 T28E1s were produced from July to August 1942, all of which had an unprotected mount for the gun combination and crew. Spotting targets was done with a M2E1 sighting system. After 80 T28E1s had been produced, the vehicle went into production with the designation M15 CGMC. Some of the T28E1s still in service were converted back into M3A1 Halftracks.

M15, M15A1, M15 "Special"
The M15 was equipped with the M42 armored weapon mount, in which two water-cooled M2 Browning machine guns were mounted above the 37 mm gun. A total of 680 M15s were produced in 1943 but because the M42 mount placed considerable stress on the M3 chassis, the M54 mount was introduced, and the resulting combination with the M3A1 Halftrack chassis was designated as the M15A1 CGMC. In August 1945, the M42 mount, and the M15 CGMC was finally classified as obsolete. The M54 gun mount reversed the places of the machine guns and 37 mm gun, and air-cooled M2 Browning machine guns replaced the water-cooled weapons used on the M15. Spotting targets was done with a M6 sighting system. A total of 1,052 M15A1s were produced in 1943, with a further 600 being produced in 1944. The unofficial name "M15 Special" relates to M15s and probably other CGMCs converted in depots in Australia to mount the Swedish-designed Bofors 40 mm gun on a halftrack chassis. This was the only successful conversion of a US halftrack to mount the Bofors gun.

Service history
The M15 was first used during Operation Torch, the Allied invasion of North Africa in November, 1942. When engaging enemy aircraft, tracer ammunition from the machine guns was used to bring the main gun onto the target. T28E1 crews claimed more than 100 aircraft kills during Operation Torch, the Battle of Kasserine Pass, and the Allied Invasion of Sicily; 39 alone were claimed at Kasserine. One T28E1 was captured by the Germans at Kasserine Pass and was later rebuilt as a carrier for equipment and troops to replace German vehicles destroyed by Allied aircraft.

Each US Army armored division was allocated an anti-aircraft artillery (AAA) company equipped with eight M15 CGMCs and eight M16 MGMCs (four Browning M2 machine guns). At corps and army level, each AAA battalion was equipped with 32 of each vehicle. After first seeing action in the Allied invasion of Italy, the M15 and M15A1 served through the rest of the Italian Campaign, the Allied invasion of Normandy and of southern France, and throughout the Western Front, including the Battle of the Bulge. They were often used in the ground support role, as Allied air superiority meant that there were few German aircraft left to engage. They were also used in the Pacific theater during the campaign to liberate the Philippines and the Battle of Okinawa. The "M15 Special" was used by the 209th AAA Battalion in the Philippines in 1944–45. The M15 and M15A1 also served in the ground-support role during the Korean War.