 Muslim Generals in Kansu waged war against the Guominjun in favor of the KMT during the conflict in Gansu in 1927–1930.Although the Second Sino-Japanese War officially broke out in 1937, Japanese aggression started in 1931 when they staged the Mukden Incident and occupied Manchuria.At the same time, the CPC had been secretly recruiting new members within the KMT government and military.