This picture shows German troops entering Poland in the fall of 1939. During this camping, Hitler introduced a new type of warfare called "Blitzkrieg" or lighting warfare. This revolutionary approach to warfare involved the use of planes, armor and vehicles to quickly overwhelm defenders within a city. Ideally a wave of bombers would damage preliminary defenses, quickly followed by tanks and other various types of armor that were intend to further weaken enemy defenses. This was followed by lightly armored soldiers typically in jeeps, half-tracks or motorcycles that began the initial primary assault. Once a strong hold or base of operations was established, greater amounts of foot soldiers would arrive and prepare for a full out assault of the city. In the initial stages of WWII Blitzkrieg was devastating to ill-equipped countries like Poland, and allowed for Hitler to quickly establish military presence in the region.