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.[333] 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.[334]
Use of armoured forces was crucial for both sides on the Eastern Front. Operation Barbarossa, the German invasion of the Soviet Union in 1941, involved a number of breakthroughs and encirclements by motorised forces. Its goal according to Führer Directive 21 (18 December 1940) was "to destroy the Russian forces deployed in the West and to prevent their escape into the wide-open spaces of Russia."[90] The Red Army was to be destroyed west of the Dvina and Dnieper rivers, which were about 500 kilometres (310 mi) east of the Soviet border, to be followed by a mopping-up operation. The surprise attack resulted in the near annihilation of the Voyenno-Vozdushnye Sily (VVS, Soviet Air Force) by simultaneous attacks on airfields,[91] allowing the Luftwaffe to achieve total air supremacy over all the battlefields within the first week.[92][93] On the ground, four German panzer groups outflanked and encircled disorganised Red Army units, while the marching infantry completed the encirclements and defeated the trapped forces.[94] In late July, after 2nd Panzer Group (commanded by Guderian) captured the watersheds of the Dvina and Dnieper rivers near Smolensk, the panzers had to defend the encirclement, because the marching infantry divisions were still hundreds of kilometres to the west.[91]
In April 1940, Rudolph Höss, who become the first commandant of Auschwitz, identified the Silesian town of Oswiecim in Poland as a possible site for a concentration camp. Initially, the camp was meant to intimidate Poles to prevent them from protesting German rule and to serve as a prison for those who did resist. It was also perceived as a cornerstone of the policy to re-colonize Upper Silesia, which had once been a German region, with “pure Aryans.” When the plans for the camp were approved, the Nazi’s changed the name of the area to Auschwitz.

In 1939, shortly after the war began, the Germans initiated the T4 Program—framed euphemistically as a “euthanasia” program—for the murder of intellectually or physically disabled and emotionally disturbed Germans who by their very existence violated the Nazi ideal of Aryan supremacy. They were termed “life unworthy of life.” An economic justification was also employed as these Germans were considered “useless eaters.” The Nazis pioneered the use of gas chambers and mass crematoria under this program. The murder of the disabled was the training ground for key personnel who were to later staff the death camps of Aktion Reinhard. The German public protested these murders. The Roman Catholic bishop of Münster, Clemens August, Graf von Galen, preached against them, and the T4 program was formally halted. Nonetheless, the murder and sterilization of these German “Aryans” continued secretly throughout the war.
Soviet civilian populations in the occupied areas were heavily persecuted.[438] Villages throughout the Soviet Union were destroyed by German troops.[439] Germans rounded up civilians for forced labor in Germany and caused famine by taking foodstuffs.[440] In Belarus, Germany imposed a regime that deported some 380,000 people for slave labor and killed hundreds of thousands of civilians. Over 600 villages had their entire populations killed, and at least 5,295 Belarusian settlements were destroyed by the Germans. According to Timothy Snyder, of "the nine million people who were in the territory of Soviet Belarus in 1941, some 1.6 million were killed by the Germans in actions away from battlefields, including about 700,000 prisoners of war, 500,000 Jews, and 320,000 people counted as partisans (the vast majority of whom were unarmed civilians)".[441] The United States Holocaust Memorial Museum has estimated that 3.3 million of 5.7 million Soviet POWs died in German custody.[442] The death rates decreased as the POWs were needed to help the German war effort; by 1943, half a million had been deployed as slave labor.[409]
After the Allied landings at Normandy, the Germans began a counter-offensive to overwhelm the landing force with armoured attacks but these failed for lack of co-ordination and Allied superiority in anti-tank defence and in the air. The most notable attempt to use deep penetration operations in Normandy was Operation Luttich at Mortain, which only hastened the Falaise Pocket and the destruction of German forces in Normandy. The Mortain counter-attack was defeated by the US 12th Army Group with little effect on its own offensive operations.[108]
The direct reason for the establishment of the camp was the fact that mass arrests of Poles were increasing beyond the capacity of existing "local" prisons. The first transport of Poles reached KL Auschwitz from Tarnów prison on June 14, 1940. Initially, Auschwitz was to be one more concentration camp of the type that the Nazis had been setting up since the early 1930s. It functioned in this role throughout its existence, even when, beginning in 1942, it also became the largest of the death camps.
"The tanks now rolled in a long column through the line of fortifications and on towards the first houses, which had been set alight by our fire. In the moonlight we could see the men Of 7th Motorcycle Battalion moving forward on foot beside us. Occasionally an enemy machine-gun or anti-tank gun fired, but none of their shots came anywhere near us. Our artillery was dropping heavy harassing fire on villages and the road far ahead of the regiment. Gradually the speed increased. Before long we were 500 -1,000 - 2,000 - 3,000 yards into the fortified zone. Engines roared, tank tracks clanked and clattered. Whether or not the enemy was firing was impossible to tell in the ear-splitting noise. We crossed the railway line a mile or so
I visited both Auschwitz 1 and 2 Birkenau in November, it was a cold, grey, miserable day. As I walked around camp 2 I couldn't speak nor could my friend. The full horror and evidence of the past was right in front of me and I still found it difficult to process. Let us never forget all those people regardless of nationality, race or gender who died but let us remember they were all someones relation.

Ghettos were intended to be temporary until the Jews were deported to other locations, which never happened. Instead, the inhabitants were sent to extermination camps. The ghettos were, in effect, immensely crowded prisons serving as instruments of "slow, passive murder."[216] Though the Warsaw Ghetto contained 30% of Warsaw's population, it occupied only 2.5% of the city's area, averaging over 9 people per room.[217] Between 1940 and 1942, starvation and disease, especially typhoid, killed many in the ghettos.[218] Over 43,000 Warsaw ghetto residents, or one in ten of the total population, died in 1941;[219] in Theresienstadt, more than half the residents died in 1942.[216]
Schlieffen's ideas were largely aimed at operational-level leaders, that is, the commanders of Germany's divisions and army corps. The biggest problems in World War One, however, were at the lower, tactical level. And the German solution to these problems was to apply Schlieffen's operational principles to small units as well as to large ones. Thus, by decentralising command and by increasing the firepower of the infantry, they created a large number of platoon-sized units capable of independent action on the battlefield.
Most of the Jewish ghettos of General Government were liquidated in 1942–1943, and their populations shipped to the camps for extermination.[349][350][t] About 42,000 Jews were shot during the Operation Harvest Festival on 3–4 November 1943.[351] At the same time, rail shipments arrived regularly from western and southern Europe at the extermination camps.[352] Few Jews were shipped from the occupied Soviet territories to the camps: the killing of Jews in this zone was mostly left in the hands of the SS, aided by locally recruited auxiliaries.[353][u]

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.