Operation Zet was a secret operation in 1937–1941 by the Soviet Union to provide military and technical resources to the Republic of China as a part of the Sino-Soviet Non-Aggression Pact. The operation aimed to help China resist the invasion of the Imperial Japanese Army during World War II. It was part of the Soviet anti-imperialist effort worldwide. In addition, the Soviet Union and the Empire of Japan had a longstanding rivalry that sometimes resulted in open hostilities.