In early December 1944 it seemed to the Americans in the Ardennes forests to be unlikely that the Germans would attack. On 16 December that illusion was shattered when the might of German Sixth Panzer Army smashed into the thinly-held US lines. The Germans led the assault with elite units of 1. SS Panzerdivision, 2. Panzerdivision and Panzer Lehr. More was to come. On 31 December Hitler launched the last German offensive in the west, Operation Nordwind. German divisions along the Lorraine front attacked into the old French Maginot Line where the Americans had dug in. With many of their reserves sent north to face the Ardennes offensive, the Americans were taken by surprise.