 The German tactic of "blitzkrieg" was initially highly effective; the Soviet air force in the western borderlands was destroyed within two days.The German Wehrmacht pushed deep into Soviet territory; soon, Ukraine, Byelorussia, and the Baltic states were under German occupation, and Leningrad was under siege; and Soviet refugees were flooding into Moscow and surrounding cities.By July, Germany's Luftwaffe was bombing Moscow, and by October the Wehrmacht was amassing for a full assault on the capital.