The German army in North Africa was defeated when Hitler split the already stretched army there. He sent half of the troops to Italy after deciding that they needed his help.
The aerial bombardment of Germany
This decreased the German morale as Britain bombed innocent residential areas as well as military targets, killing citizens. British and American planes also adopted area bombing. They dropped around 72,000 tonnes of bombs on Germany; large sections of cities were targeted and bombed to destruction. Aerial bombing offered the only chance to bring the war to Germany itself and Britain was the only country left in Europe with the military strength to do it. Although bombing restricted rather than wiped out German war production, it also forced the Germans on to the defensive. They had to divert nearly one million men and 55,000 artillery guns to defend the German homeland against Allied bombing. Also, German aircraft factories, which were specifically targeted by Bomber Command and the USAAF, had to concentrate on producing fighters for defense against the bombing onslaught, instead of producing more bombers for attack. Without bombing, those valuable resources could have been used elsewhere to great effect (e.g. to support the German army on the Russian front, or to launch a second invasion attempt on Britain). Albert Speer, Hitler’s Armaments Minister, said that the bombing of Germany was ‘the greatest lost battle on the German side’.
Battle of the Atlantic
The conflict at sea between Allied merchant ships and their escorts and German U-boats, christened the Battle of the Atlantic by Winston Churchill on 6 March 1941, was arguably the decisive campaign of the Second World War. Only the clash of massed German and Soviet armies on the Eastern Front was as influential in its outcome. To survive, Britain needed imports of food, fuel and raw materials from overseas. If Britain had fallen, there would have been no base for the western Allies to launch a strategic air offensive or a land invasion of the European mainland to defeat Germany and Hitler would have been free to concentrate all his resources against the Soviet Union. The allies were badly damaged by the U-boat campaign however, very effective Allied counter-measures including the introduction of escort support groups, some with aircraft carriers, and Very Long Range aircraft to close the air gap in mid-Atlantic quickly brought a decisive end to the U-boat threat. Although U-boats would continue to operate until the end of the war, the Germans had lost the Battle of the Atlantic by the end of May 1943.
Opening of Western Front in 1944.
Following the successful D-Day landings in June 1944, the Americans liberated the Loire valley, Paris and Liege. Germany was being forced backwards towards Berlin. America and Britain had used the element of shock and surprise after the Normandy landings to drive the weakening Germans back.
Superior resources of the allies.
Throughout WW2 the allies had superior supplies to Germany, British planes were more modern and had better technology and the radar system was far more advanced, this gave Britain an advantage. The allies also had more organised leaders who were less power hungry and not over ambitious. Once the U.S.A joined the war, the allies had larger quantities of superior resources, including extra planes, ships and troops.