The purpose of this thesis is to examine the negotiations which culminated in the Nazi-Soviet Nonaggression Pact of 1939 and to point out the factors which led Hitler to make two great reversals of policy. The first momentous reversal occurred in 1939 when Hitler, despite his furious rantings in Mein Kampf and in his speeches against the "Judeo-Bolsheviks" decided, contrary to his previous plans, to undertake definite negotiations for a nonaggression pact of the Soviet Union. The course of the negotiations is described in detail and the progress of German-Soviet relations after the signing of the pact is also reported.