Designed by Bliss-Leavitt and available in 1911, the Mk 8 was the second steam-powered USN destroyer torpedo, and also the first U.S. torpedo to be designed with a diameter of 21" (533mm). Most delivery vehicles originally designated for the Mk 8 had already been discarded at the outbreak of World War II, but the destroyers of the Wickes and Clemson classes all retained their many torpedo tubes. Each of them carried twelve tubes of short dimensions that were unable to carry the more modern but ineffective Mk 15, forcing them to use the Mk 8. The only units engaging the enemy with these weapons were ships of the Asiatic Fleet in the Battle of Balikpapan in January 1942, the first surface action the Navy fought since 1898. Three transports were sunk by Mk 8 torpedos. During the small engagement in Bandoeng Strait, or so Van Oosten claims, destroyer Michishio suffered hits from Pillsbury's Mk 8s, but this could not be confirmed. During the Battle of the Java Sea, the last engagement for the Mk 8, the Japanese never staggered into range.

    After the old fourstack destroyers were rebuild to fit different roles, the Mk 8 was primarily used by PT boats. Britian received a number of these torpedos with the fifty old destroyers transfered to the kingdom in 1940. Some may have been used by U.S. submarines during the 1942 torpedo crisis, when torpedos were in short supply. This is speculation, however.