Second Army crossed the Rhine on 23 March in an attack codenamed Operation Plunder. It then headed across the North German Plain towards Osnabrück, with the First Canadian Army on its left wheeling to clear the north of the Netherlands and the area of Lower Saxony west of Oldenburg. The US Ninth Army on its right turned south-east towards Lippstadt to trap the German Army Group B, under General Walther Model, in an enormous pocket in the Ruhr. With Army Group B trapped, the last major German formation in the west had been neutralized.