The Government of the German Reich and The Government of the Union of Soviet Socialist Republics
Desirous of strengthening the cause of peace between Germany and the U.S.S.R., and proceeding from the fundamental provisions of the Neutrality Agreement concluded in April, 1926 between Germany and the U.S.S.R., have reached the following Agreement:
Article I. Both High Contracting Parties obligate themselves to desist from any act of violence, any aggressive action, and any attack on each other, either individually or jointly with other Powers.
[...]
From a Secret Additional Protocol:
Article II. In the event of a territorial and political rearrangement of the areas belonging to the Polish state, the spheres of influence of Germany and the U.S.S.R. shall be bounded approximately by the line of the rivers Narev, Vistula and San.
The question of whether the interests of both parties make desirable the maintenance of an independent Polish States and how such a state should be bounded can only be definitely determined in the course of further political developments.
In any event both Governments will resolve this question by means of a friendly agreement.
Moscow, August 23, 1939.
Nazi-Soviet Relations 1939-1941. Documents from the Archives of the German Foreign Office, Washington D.C., 1948