Throughout 1938-1939, the Soviet military functionaries assumed that the most probable security threat for the USSR came not only from a military union of Germany and Italy, but also from Poland, which appeared in the “orbit” of the Nazi block. Thus, the USSR had to be prepared for a fight on two fronts – in the West (against Germany and Poland) and in the East (against Japan).
This message is part of the Kremlin’s policy of historical revisionism – it tries to explain the necessity of signing of the Ribbentrop-Molotov Pact and German and Soviet attacks on Poland in September 1939 by alleged “military threats” coming from Poland. See other examples referring to the Ribbentrop-Molotov Pact here, here and here. The accusation of Poland as posing a “military threat” for the USSR is a clear historical manipulation. Before WWII, Poland had tense political relations with Nazi Germany, which had open territorial claims to Poland (revision of the status of the Free City of Danzig and control over the “Polish Corridor”). Despite intense political pressure from Hitler, Poland refused to become a part of the Nazi block. See similar examples of the Russian historical revisionism concerning Poland here and here.