[4] The unit moved from Langley where it trained initially, to Borinquen Field, Puerto Rico, where it became part of Caribbean Air Force on 1 November 1940.

The squadron participated in various training and familiarization flights with its small complement of Douglas B-18 Bolo medium bombers, until 8 November 1941 when it was ordered to deploy to Benedict Field, St. Croix, temporarily until September 1942, then at St. Nicholas, and Antigua.

By mid-February, these had been augmented by a further B-18 (while one of the B-18As was away at the Mobile Air Depot being fitted with one of the earliest airborne radar systems) and the squadron had a total of four crews, three of whom had more than 12 months experience.

Apparently this aircraft dispersal proved too much for the unit to handle and, by January 1943, strength on report had dropped to a more reasonable total of just five B-18Bs and a single B-18C at Dakota Field, although Flight D remained at Borinquen as late as June, and Flight C moved from Dakota to Rio Hato Field, Panama, from 1 June till 20 July 1943.

As the antisubmarine campaign eased, the unit became, essentially, a crew training outfit, although patrols were still flown in conjunction with this tasking.

"Eleven years later, on [1 September] 1955, the 12th Bombardment Squadron, Medium, was activated at Abilene Air Force Base, Texas.

This reorganization took the three combat disciplines, ICBM operations, security police, and electromechanical maintenance, and combined them under the "one hat" of the missile squadron commander.