A6M2a Type 11 - first Zero version went into operation with the 12th Rengo Kōkūtai (Combined Air Group 聯合航空隊) in July 1940. On 13 September 1940, the Zeros scored their first air-to-air victories when 13 A6M2s led by Lieutenant Saburo Shindo attacked 27 Soviet-built Polikarpov I-15s and I-16s of the Chinese Nationalist Air Force (Republic of China Air Force (ROCAF) 1937~1945, formed by Kuomintang 國民黨), shooting down all the fighters without loss.