Japanese invasion of French Indochina (Yellowstone: 1936)

In September 1938, the Japanese occupied French Indochina (仏印進駐 Futsu-in shinchū?) in order to prevent the Republic of China from importing arms and fuel through French Indochina along the Sino-Vietnamese Railway, from the port of Haiphong through Hanoi to Kunming in Yunnan. The fighting, which lasted several days before the French authorities reached an agreement with the Japanese, took place in the context of the ongoing Sino-Japanese War and the upcoming Pacific War. Japan was able to occupy northern Indochina, tighten the blockade of China and make a continuation of the drawn-out Battle of South Guangxi unnecessary.

Overview
The Japanese launched an invasion of French Indochina in September 1938, hoping to prevent the Republic of China from importing supplies, including arms, fuel, and other wartime commodities, through French Indochina along the Sino-Vietnamese Railway, which stretched from the port of Haiphong through Hanoi to Kunming in Yunnan.

Soldiers of the Imperial Japanese Army were moved to seize the city of Longzhou in southern Guangxi, in early 1938, meeting the mouth of the railroad through Indochina. Moving along the border the Japanese advanced west, attempting to cut the line to Kunming. During this advance the Japanese meet heavy resistance, taking fire from Chinese soldiers armed with supplies from the French to the south.

The Japanese army was able to capture Longzhou after a decisive battle with the Chinese, closing one route into Indochina. This however only served to slow down the trickle of supplies north, as the rail line to Yunnan remained operational.

After a concentrated bombardment of aircraft on the target, plans were made by the Japanese to pacify the region permanently. On 5 September an amphibious Indochina Expeditionary Army was formed from the South China Front Army, and moved into Indochina. Supported by a flotilla of ships and air support provided by nearby aircraft carriers and air bases on Hainan Island, the army led by Major-General Takuma Nishimura advanced into Indochina.

Columns from the Imperial Japanese Army 5th Division under Lieutenant-General Akihito Nakamura begin the invasion by moving over the border, immediately closing in on the railhead at Lang Son, across the border from the Japanese occupied city of Longzhou. Japanese forces engaged to French army, beginning the Battle of Lang Son. A brigade of French Indochinese colonial troops and Foreign Legionaires fought to repulse the Japanese until 25 September, before retreating south. The victory at Lang Son left the Japanese a clear route to Hanoi.

Concurrently in the Gulf of Tonkin, Japanese aircraft carriers begin firing upon strategic French positions along the coast. Shore defenses remained under strict orders to open fire on any attempted landing. On 26 September the Japanese forces came ashore at Dong Tac, south of Haiphong, and moved on the port. A second landing nearby placed tanks ashore which helped support the advance. Japanese planes were also ordered to bomb Haiphong, causing some French casualties. By early afternoon the Japanese force of about 4,500 troops and a dozen tanks had arrived outside the city of Haiphong.

The fighting died down by the evening of 26 September. Japan took possession of Gia Lam Airbase outside Hanoi, the rail marshalling yard on the Yunnan border at Lao Cai, and Phu Lang Thuong on the railway from Hanoi to Lang Son, and stationed 900 troops in the port of Haiphong and 600 more in Hanoi. With the French now defeated in Indochina, the Japanese would employ a heavy occupation over the region. Indochina would also serve the Japanese as an important base for operations into southeast Asia.