Defensively equipped merchant ship
![](/Images/godic/202501/08/INF3-127_War_Effort_Under_the_Red_Duster_they_sustain_our_Island_Fortress3317.jpg")
![The gun crew of a defensively equipped merchant ship during a drill at Halifax, Nova Scotia in 1942. A merchant seaman is passing a shell to the Royal Navy gunners.](/Images/godic/202501/08/QF_4_inch_Mk_IV_gun_&_crew_1942_LAC_35723673317.jpg")
![The US passenger steamer SS Kroonland in November 1917, showing camouflage paint and stern-mounted gun.](/Images/godic/202501/08/SS_Kroonland,_rear,_Nov_19173317.jpg")
![BL 4 inch Mk VII low-angle gun on a DEMS in 1943, an obsolete WWI gun typical of WWII DEMS armament](/Images/godic/202501/08/BL_4_inch_Mk_VII_gun_DEM_1943_LAC_33945083317.jpg")
Defensively equipped merchant ship (DEMS) was an Admiralty Trade Division program established in June, 1939, to arm 5,500 British merchant ships with an adequate defence against enemy submarines and aircraft. The acronym DEMS was used to describe the ships carrying the guns, the guns aboard the ships, the military personnel manning the guns, and the shore establishment supporting the system.