The Northern Army Group (NORTHAG) was a NATO military formation comprising five Army Corps from five NATO member nations. During the Cold War NORTHAG was NATO's forward defence in the Northern half of the Federal Republic of Germany (FRG). The Southern half of the Federal Republic of Germany was to be defended by the four Army Corps of NATO's Central Army Group (CENTAG). During wartime NORTHAG would command four frontline corps (I Dutch, , I British, I Belgian) and one reserve corps (III US). Air support was provided by Second Allied Tactical Air Force.