The D3A1 first saw combat operation in November 1939, one month prior to its official acceptance as the Navy Type 99 dive bomber. Nakajima sent several examples to 14th Air group operating at Haikou on Hainan island in South China. These D3A1 were commanded by Lieutenant Sadamu Takahashi and supported the Imperial Japanese Army in the capture of Nanning, which was intended to cut the supplies coming from French Indochina. After the capture of Nanning, they continued to be operated in the area in 1940. In May 1940, 12th Air Group became the second front-line unit to be equipped with the new D3A1 dive bombers. They first participated in the capture of Yichang and conducted anti-shipping operations on Yangtze river, west of Yichang, in order to cut the Chinese supplies coming from Chongqing. In September, D3A1 from the 12th Air Group started to fly missions against Chongqing, which was the Chinese capital at the time. After the invasion of Indochina in autumn 1940, 14th Air Group operated at Hanoi and flew missions against Kunming and Burma Road.