At the same time, the German Nineteenth Army, retreated northward through the Rhône valley toward the Plateau de Langres where it was joined by the German Fifth Panzer Army which was assigned to Army Group G so that a counter-attack could be delivered against the United States Third Army.[3] The retreat did not go according to plan, as the Nineteenth Army retreated many personnel of Army Group G were taken prisoner by the Sixth United States Army Group.[4] By the time the retreat was over General Johannes Blaskowitz had lost about half his force and was relieved on 21 September by General Hermann Balck.[5] By mid September the Fifth were in position on the left wing of the German line north of the Swiss border.