 By March 1945 , the Allied armies had advanced into Germany and had reached the River Rhine . The Rhine was a formidable natural obstacle to the Allied advance , but if breached would allow the Allies to access the North German Plain and ultimately advance on Berlin and other major cities in Northern Germany . Following the " Broad Front Approach " laid out by General Dwight David Eisenhower , the Supreme Allied Commander of the Allied Expeditionary Force , it was decided to attempt to breach the Rhine in several areas . Field Marshal Sir Bernard Montgomery , commanding the Anglo @-@ Canadian 21st Army Group , devised a plan , code @-@ named Operation Plunder , that would allow the forces under his command to breach the Rhine , which was subsequently authorized by Eisenhower . Plunder envisioned the British Second Army , under Lieutenant @-@ General Miles C. Dempsey , and the U.S. Ninth Army , under Lieutenant General William Simpson , crossing the Rhine at Rees , Wesel , and an area south of the Lippe Canal . 
