Japanese Imperial General Headquarters Gives Order for Japanese Troops to Invade French Indochina

The Japanese Invasion of French Indochina (仏印進駐 Futsu-in shinchū?), also known as the Vietnam Expedition, was an attempt by the Empire of Japan, during the Second Sino-Japanese War to blockade China and prevent it from importing arms, fuel and 10,000 tons/month materials supplied by the United States through the Haiphong-Yunnan Fou railway line. Control of Vichy-controlled French Indochina would make the blockade of China more effective and made continuation of the drawn out Battle of South Guangxi province unnecessary.

On 11 Sep, Japanese Army Major General Issaku Nishihara, who had previously signed the 4 Sep agreement with Martin, reported to Tokyo that it was his opinion that the French would continue to drag on the negotiations. On 14 Sep, the Imperial General Headquarters gave the orders for troops to move into Indochina on 22 Sep, regardless of the state of the negotiations. The date was chosen as the day after when the Tripartite Pact was originally scheduled to be signed; Matsuoka thought that, with Germany and Italy as Japan's allies at that point, the US would be even less likely to react militarily to an invasion of Indochina. Additionally, Japanese intelligence concluded that the Chinese, worried about having the Indochina supply line being severed, were planning on an excursion into Indochina to secure key road junctures and railways.