During the war, the Hydramatic was used in a variety of military vehicles, including the M5 Stuart tank (where two of them were mated to twin Cadillac V8 engines) and the M24 Chaffee light tank. The extensive wartime service greatly improved the postwar engineering of the transmission, later advertised as "battle-tested."
That’s the Chaffee, I believe. It was named after Adna Chaffee, known as “the Father of the Armored Force.” Heard of Fort Chaffee? Named after him as well.
Oh: it's an automatic transmission. You really don't want to have to work the clutch when you're under fire.