In November 1944, both defensive lines were broken and the First Army retreated to the German border and defended the Saarland of Germany, an important industrial region. With the Third U.S. Army engaged to the north against the German Ardennes Offensive, the 1st Army attacked the Seventh U.S. Army on New Year's Day 1945 in Operation Nordwind, causing the Americans to give ground and inflicting significant casualties where Seventh U.S. Army defensive lines were stretched taut by the length of frontage they had to cover. With the failure of Nordwind in late January, the 1st Army was first pushed back to the Siegfried Line and then forced to retreat across the Rhine River when the Allies pierced the German fortifications.