What gun used 37mm shells?

Answer 1

The American infantry used an anti-take weapon that was the 37-mm Anti-Tank gun. Later, they adopted a 57-mm AT gun. These were light weapons which could be pulled by infantrymen. Each Infantry Regiment of an Infantry Division had one Anti-Tank Company and one Cannon Company, which could be used for direct support. However, they were primarily used as a defense in case infantry had to fall back.
Each Infantry Regiment had one Field Artillery Battalion for direct fire support which fired the 105mm Howitzer.