Term | Explanation |
| Capital | Operational code name for the recapture of northern Burma in 1944. |
| Case Green | Operational code name for the intended German military invasion of Czechoslovakia. |
| Case Red | Operational code name for counterstrike against France in the event of an attack on Germany from the West. |
| Case White | Operational code name for the German invasion of Poland. |
| Case Yellow | Operational code name for the German invasion of the Netherlands, Belgium and France. |
| Catapult | Operational code name for the destruction of the French Fleet by the British in North Africa, July 1940. |
| Catchpole | Operational code name for the US assault on the Marshall Islands, 1944. |
| CCS | Combined Chiefs of Staff (Allies). |
| Chain Home | British air-defence radar. |
| Chindits | Long-range penetration troops (British and Gurkha) who worked behind the Japanese lines in Burma. |
| CIGS | Chief of the Imperial General Staff (British) |
| Citadel | Operational code name for the German attack on the Soviet forces near Kursk, July 1943. |
| Cobra | Operational code name for the American breakout from Normandy in July 1944. |
| Cockade | Operational code name for Allied deception operations intended to draw attention away from Normandy prior to D-Day. |
| Comintern | Communist International organisation created to promote the spread of communism from the Soviet Union - disbanded in 1943. |
| Commando Supremo | Italian supreme command. |
| Compass | Operational code name for British operations in Egypt against the Italians in December 1940. |
| Crossbow | Operational code name for Allied attacks on V-1 launch sites. |
| Crusader | Operational code name for British attempts to relieve Torbruk beginning in November 1942. |