The M4 Sherman, officially Medium Tank M4, was the most widely used medium tank by the United States and Western Allies in World War II. The M4 Sherman proved to be reliable, relatively cheap to produce, and available in great numbers.
The Rocket Launcher T34 (Calliope) was a tank-mounted multiple rocket launcher used by the United States Army during World War II. The launcher was placed atop the M4 Sherman, with its prominent vertical side frames anchored to the turret's sides, and fired a barrage of 4.5 in (114 mm) M8 rockets from 60 launch tubes. It was developed in 1943; small numbers were produced and were used by various US armor units in 1944–45. It adopts its name from the musical instrument "Calliope", also known as the steam organ, which had similar parallel or clustered pipes.