What an armed merchant cruiser could actually do

Armed merchant cruisers were merchant ships with guns, not cruisers in the military sense. They could patrol long distances, deter or confront converted raiders, and give the Royal Navy more eyes when aircraft and satellites were unavailable. Their lack of armour, speed, subdivision, and torpedo protection made them highly vulnerable to submarines and purpose-built surface combatants. They belonged in secondary or tertiary roles, where their risks became tolerable only because global war created more patrol and escort demands than regular warships could fill. The modern comparison warns against placing critical missile systems on similarly unprotected commercial hulls.