日ソ中立条約
Matsuoka also signed the Soviet–Japanese Neutrality Pact during his visit to Moscow in April 1941. However, after Nazi Germany's invasion of the Soviet Union in June 1941, Hitler proposed to Matsuoka that Japan take part in the attack as well. Matsuoka became a fervent supporter of the idea of a Japanese attack on Siberia, and constantly pressured Konoe and the leaders of the Imperial Japanese Army and Imperial Japanese Navy to mobilize the military for that purpose. In the end, both the army and the navy as well as Konoe decided to concentrate military efforts on targets south of Japan.