 As commander, Ueda supported measures to suppress the illicit narcotics trade in Manchukuo and northern China.In 1939, he also held the post of ambassador of Japan to Manchukuo and was a member of the Supreme War Council.A strong believer in the “Strike North” or "Hokushin-ron" policy that Japan's main enemy was communism and that Japan's destiny lay in conquest of the natural resources of the sparsely populated north Asian mainland, Ueda supported the unauthorized aggressive actions initiated by staff and field officers on the Soviet border with Manchukuo and Mongolia which lead to the Soviet–Japanese border conflicts with heavy fighting and high casualties against Soviet forces around Nomonhan between May and August 1939.