Allied air superiority became a significant hindrance to German operations during the later years of the war. By June 1944 the Western Allies had complete control of the air over the battlefield and their fighter-bomber aircraft were very effective at attacking ground forces. On D-Day the Allies flew 14,500 sorties over the battlefield area alone, not including sorties flown over north-western Europe. Against this on 6 June the Luftwaffe flew some 300 sorties. Though German fighter presence over Normandy increased over the next days and weeks, it never approached the numbers the Allies commanded. Fighter-bomber attacks on German formations made movement during daylight almost impossible. Subsequently, shortages soon developed in food, fuel and ammunition, severely hampering the German defenders. German vehicle crews and even flak units experienced great difficulty moving during daylight.[g] Indeed, the final German offensive operation in the west, Operation Wacht am Rhein, was planned to take place during poor weather to minimize interference by Allied aircraft. Under these conditions it was difficult for German commanders to employ the "armoured idea", if at all.
For historical generals, from Alexander the Great of ancient Macedonia to Frederick II of 18th-century Prussia, their armies functioned as the centre of gravity. If the army was destroyed, the commander would be considered a failure. In smaller countries or countries engaged in internal strife, according to Clausewitz’s reasoning, the capital becomes the centre of gravity and should be identified as the Schwerpunkt. Beginning in the 20th century, technological advances such as radio, aircraft, and motorized vehicles allowed a commander to concentrate force at the Schwerpunkt so as to annihilate the opposition and achieve victory. During World War II each blitzkrieg campaign contained a Schwerpunkt that gave it meaning and substance, with doctrines of mobile warfare expounded by British military theorists J.F.C. Fuller and Sir Basil Liddell Hart providing the tactics necessary to translate the theory into action.
The Polish government-in-exile in London learned about the extermination camps from the Polish leadership in Warsaw, who from 1940 "received a continual flow of information about Auschwitz", according to historian Michael Fleming. This was in large measure thanks to Captain Witold Pilecki of the Polish Home Army, who allowed himself to be arrested in Warsaw and spent 945 days in Auschwitz from September 1940 until April 1943, organizing the resistance movement inside the camp.
By July 1944, Germany was losing the war; the SS began closing down the easternmost concentration camps and deporting the remaining prisoners westward. Many were killed in Auschwitz and the Gross-Rosen concentration camp. Schindler convinced SS-Hauptsturmführer Amon Göth, commandant of the nearby Kraków-Płaszów concentration camp, to allow him to move his factory to Brněnec in the Protectorate of Bohemia and Moravia, thus sparing his workers from almost certain death in the gas chambers. Using names provided by Jewish Ghetto Police officer Marcel Goldberg, Göth's secretary Mietek Pemper compiled and typed the list of 1,200 Jews who travelled to Brünnlitz in October 1944. Schindler continued to bribe SS officials to prevent the execution of his workers until the end of World War II in Europe in May 1945, by which time he had spent his entire fortune on bribes and black market purchases of supplies for his workers.