The Merchant Marine is the fleet of ships which carries imports and exports during peacetime and becomes a naval auxiliary during wartime to deliver troops and war materiel. The Government trained the men to operate the ships and assist in manning the guns through the U.S. Maritime Service.
Mariners is the preferred designation.
The term Merchant Marines is also incorrect although it is even used by some old time mariners. The ship shall be defended by her armament, by maneuver, and by every available means as long as possible. When, in the judgment of the Master, capture is inevitable, provision should be made to open sea valves and to flood holds and compartments adjacent to machinery spaces, start numerous fires and employ any additional measures available to insure certain scuttling of the vessel. Merchant mariners were subject to the draft if they took more than 30 days shore leave. Experienced mariners who had been drafted were released by the Army to serve in the Merchant Marine.