germany's immediate preparations for the attack against its eastern neighbor had been ongoing since the oberkommando der wehrmacht issued the "directive for the uniform preparations of the armed forces for the war for 1939-40" between 3 april and 10 may 1939. the political background for the conflict goes quite a bit further. the signing of the molotov–ribbentrop pact between germany and the soviet union on 23 august 1939 created the immediate political prerequisites for germany to launch its invasion.