Term | Explanation |
| Jael | Operational code name for the Allied deception operations in Europe - later called Plan Bodyguard. |
| JCS | Joint Chiefs of Staff - US high command, representing US Army and Navy. |
| JIC | Joint Intelligence Committee - Top intelligence body in both USA and UK. |
| JPS | Joint Planning Staff - British military planning organization. |
| JSC | Joint Security Control - US organization, subordinate to the JCS responsible for security/codebreaking/deception operations. |
| Jubilee | Operational code name for the British-Canadian raid on Dieppe - August 1942. |
| Juno | Operational code name for one of the D-Day landing areas in Normandy between the Provence River and the town of St. Aubin sur Mer - principally a Canadian landing area. |
| Jupiter | Operational code name for British plan to invade Norway. |