Four destroyers in the United States Navy comprised the Cassin class. All served as convoy escorts during World War I. The Cassins were the first of five "second-generation" 1000-ton four-stack destroyer classes that were front-line ships of the Navy until the 1930s. They were known as "thousand tonners" for their normal displacement, while the previous classes were nicknamed "flivvers" for their small size, after the Model T Ford.
USS Cassin in Coast Guard service
The 4″/50 caliber gun was the standard low-angle, quick-firing gun for United States, first appearing on the monitor Arkansas and then used on "Flush Deck" destroyers through World War I and the 1920s. It was also the standard deck gun on S-class submarines, and was used to rearm numerous submarines built with 3-inch (76 mm) guns early in World War II. United States naval gun terminology indicates the gun fired a projectile 4 inches in diameter, and the barrel was 50 caliber. 4x50 meant that the barrel was 200 inches long, or 16 feet long.
The gun from USS Ward which fired the first American shot of World War II at Pearl Harbor on 7 December 1941 at the State Capitol grounds in St. Paul, Minnesota.