Heeresgruppe Nord
By 25 August 1939, Bock was in command of Army Group North in preparation for the invasion and conquest of Poland. The objective of Army Group North was to destroy the Polish forces north of the Vistula. Army Group North was composed of General Georg von Küchler's 3rd Army, and General Günther von Kluge's 4th Army. These struck southward from East Prussia and eastward across the base of the Polish Corridor, respectively.