Overview: D-Day, the successful Allied landing in Normandy on June 6, 1944, heralded the final phase of the Second World War: But even after securing their bridgeheads in France, the American, British and Canadian units faced further enormous sacrifices. Operation Cobra, an offensive near Caen supported by massive bombing, weakened the German lines enough for the Allies to achieve a breakthrough. From August 1944 they were able to consolidate their troops and at the same time advance towards Paris, despite bitter German resistance.