policy carried out by germany using a strategy called blitzkrieg
Blitzkrieg (German, "lightning war" listen (help info)) is a method of warfare whereby an attacking force, spearheaded by a dense concentration of armoured and motorised or mechanised infantry formations with close air support, breaks through the opponent's line of defence by short, fast, powerful attacks and then dislocates the defenders, using speed and surprise to encircle them. Through the employment of combined arms in manoeuvre warfare, blitzkrieg attempts to unbalance the enemy by making it difficult for it to respond to the continuously changing front, then defeat it in a decisive Vernichtungsschlacht (battle of annihilation).