The generally accepted definition of blitzkrieg operations include the use of maneuver rather than attrition to defeat an opponent, and describe operations using combined arms concentration of mobile assets at a focal point, armour closely supported by mobile infantry, artillery and close air support assets. These tactics required the development of specialized support vehicles, new methods of communication, new tactics, and an effective decentralized command structure. Broadly speaking, blitzkrieg operations required the development of mechanized infantry, self-propelled artillery and engineering assets that could maintain the rate of advance of the tanks. German forces avoided direct combat in favour of interrupting an enemy's communications, decision-making, logistics and of reducing morale. In combat, blitzkrieg left little choice for the slower defending forces but to clump into defensive pockets that were encircled and then destroyed by following German infantry.
Tens of thousands of Jews held in the eastern territories were marched towards the heart of Germany so they could not bear witness to the Allies. Aware that the world had been alerted to the horrors of the camps, the Nazis sought to destroy evidence. In June, Soviet forces liberated the first major camp, known as Majdanek, in Lublin, Poland. The Nazis had burned down the crematorium chimney but had failed to destroy the gas chambers and barracks. Only a few hundred inmates were still alive.
At Auschwitz I, the majority of the complex has remained intact. The architecture of the camp consisted mostly of pre-existing buildings converted by the Nazis to serve new functions. The preserved architecture, spaces and layout still recall the historical functions of the individual elements in their entirety. The interiors of some of the buildings have been modified to adapt them to commemorative purposes, but the external façades of these buildings remain unchanged.