The correct answer is C, as the invasion was key in forcing the Germans to retreat to the East.
The decision to undertake an invasion through the English Channel in 1944 was made at the Trident Conference in Washington DC, in May 1943. US General Dwight D. Eisenhower was appointed commander of the Supreme Headquarters of the Allied Expeditionary Force ( SHAEF) and British General Bernard Montgomery commander of the XXIst Army Group, which brought together all the ground forces that would take part in the invasion. The chosen place was the coast of the French region of Normandy, where five beaches were selected which were given code names: Utah and Omaha, which would be attacked by the Americans, Sword and Gold, target of the British, and the beach Juno, place of disembarkation of the Canadians. The French ports were strongly defended, which led to the creation of two artificial piers, called Mulberry, and specially modified tanks were used to overcome the difficulties expected on the beaches. In the months prior to the operation, the Allies carried out an elaborate military distraction maneuver, Operation Bodyguard, using both electronic and visual disinformation. With this they managed to avoid that the Germans knew the date and location of the landings. Adolf Hitler had commissioned the reputed field marshal Erwin Rommel to supervise and improve a chain of coastal fortifications known as the Atlantic Wall, in anticipation of the enemy attack.
The Allies were not able to achieve the objectives planned for the first day, but they did secure a precarious beachhead that they expanded tenaciously in the following days, with the capture of the port of Cherbourg on June 26 and the city of Caen on the July 21. The German counterattack on August 8 failed and left 50,000 soldiers of the VII Army of the Wehrmacht trapped in the so-called Falaise bag. On August 15, the Allies launched an invasion of southern France, Operation Dragoon, and on August 25 the Liberation of Paris took place. German forces withdrew through the Seine river valley on August 30, marking the end of Operation Overlord.
