The XIX Panzerkorps (General Heinz Guderian) was to advance to the French border with Switzerland and trap the French forces in the Vosges Mountains while the XVI Panzerkorps attacked the Maginot Line from the west, into its vulnerable rear to take the cities of Verdun, Toul and Metz. The French had moved the 2nd Army Group from the Alsace and Lorraine to the Weygand line on the Somme, leaving only small forces guarding the Maginot line. After Army Group B had begun its offensive against Paris and into Normandy, Army Group A began its advance into the rear of the Maginot line.