 A third corps, the XXI (Maj. Gen. Frank W. Milburn), was relatively new, having joined the army in January.As the Seventh Army offensive began, the basic question was how stubbornly the Germans would defend before falling back on the Siegfried Line.Only General Milburn's XXI Corps — on the Seventh Army's left wing, near Saarbrücken — was fairly close to the Siegfried Line, while other units were as much as away.