Contributor: C. Peter Chen
When Japan brought Asia into World War II in 1937 with the invasion of China, the general feeling among top Japanese leadership was that China could be defeated within two to three years. However, by mid-1940, the Chinese not only held their ground, but also tied down a significant portion the Japanese Army's resources. Japan partially attributed the delay of schedule to western powers providing China weapons and supplies via British Burma and French Indochina. The completion of the German conquest of France in Jun 1940 provided Japan an opportunity to sever one of the two supply routes into China. Shortly after the establishment of the Vichy government in France, Japan began demanding the right to station troops in Indochina, but Japan had to do it in a manner so not to arouse too much attention from the United Kingdom and the United States. On 17 Jul, the UK announced that the Burma Road would be closed; as the UK was busy preparing for a possible German invasion, it was appeasing Japan since it could not spare much resources to bolster the defense of her holdings in Asia. Japanese intelligence learned that the Americans also did not wish to become involved in affairs in Asia, but the US seemed to be slightly tougher diplomatically than the UK.
Across the South China Sea, Douglas MacArthur and Manuel Quezon in the Philippine Islands were alarmed, as the Japanese demands seemed to be signaling preparations for a further invasion. In Washington DC, United States, on 26 Jul, US President Franklin Roosevelt passed executive orders to freeze all Japanese and Chinese assets, forbade the export of oil, iron, and rubber to Japan, as well as marking the Panama Canal off-limits to Japanese shipping. At Roosevelt's request, Britain and Holland also applied similar embargoes against the Japanese. Japan saw this as an insult from the western world, and this western reaction perhaps sealed the future for war.
On 27 Jul 1940, the Japanese Imperial General Headquarters officially decided to pursue a southern advance, thus Indochina, with "the best natural harbor in the Orient", said William Manchester, gained more importance to the Japanese. While the Japanese Army wished to simply march into Indochina, the Navy and the Foreign Ministry were able to hold off the Army advance while continuing diplomatic negotiations. On 1 Aug, Foreign Minister Yosuke Matsuoka asked French Ambassador to Tokyo Arsène Henry whether Japanese troops might be allowed to enter Indochina to occupy certain airfields; Henry implied that his government would reject such a request. Regarding this request, French Foreign Minister Paul Baudouin noted France's unfavorable position:
While Japan negotiated with France, the military was already on the move: Starting on 1 Aug, Army aircraft were being transferred from Taiwan and Northern China to the South China Force. The French, who lacked the military prowess to influence the negotiations, tried to drag the negotiations for as long as they could, hoping that the US and the UK would interfere.
On 7 Aug, Lord Halifax of the UK voiced UK's concern for the Japanese demands for Indochina; on the same day, US Ambassador to Tokyo Joseph Grew also expressed similar notions on behalf of his government. Both notes lacked the strong language that was necessary to deter Japan, and the Japanese continued to push the demands. Sensing lack of decisive support from the US and the UK, Henry officially gave in to Japanese demands on 30 Aug, allowing 6,000 Japanese troops to enter Indochina.
However, even at this point, the French continued to conduct the negotiations as slowly as possible. On 4 Sep, French Army General Maurice Martin took over negotiations, signing a further agreement with the Japanese, thus the situation began to appear to go in favor of Japan. However, on the next day, Martin was informed that Japanese troops had crossed the borders into Indochina before the negotiations concluded, and Martin immediately suspended all talks. On the same day, Japanese intelligence intercepted two French diplomatic messages. The first was to the United States, detailing the Martin-Nishihara Agreement of 4 Sep 1940, which signaled to the Japanese that the US was still involved in the matter. The second the French request for British military assistance. With this information, the Japanese Army argued that force must now be used to occupy Indochina before American and British forces arrive, but the Japanese Navy continued to assert that, especially knowing that the US and the UK were still playing a part in Indochina affairs, the matter must be concluded by diplomatic and peaceful means. With the UK deeply threatened by the Battle of Britain and an isolationist Congress in the US, they continue to show little solid support for France.
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.
On 17 Sep 1940, negotiations resumed. The Japanese delegation suddenly started to demand more than what was tentatively agreed upon between Martin and Nishihara on 30 Aug, increasing the number of allowed troops from 6,000 to 25,000 and the use of airfields from three to five. The delegation openly said that "[w]e will advance into French Indo-China forcibly, unless the French accept our demands."
The 14 Sep order from IGHQ was intercepted by British intelligence, but it was not deciphered until 20 Sep, thus it gave the British only two days to react to the Japanese invasion. With no time to muster any military force to potentially discourage the Japanese advance, all the British could do was continuing to protest via diplomatic messages. The US, too, continue to protest, but failed to commit any further assistance for the French.
On 22 Sep, during negotiations, Martin agreed to the extended Japanese demands, the only success was the decrease of total number of Japanese troops allowed to be stationed in Indochina. On the next day, however, the Japanese 5th Division under the command of Lieutenant General Akihito Nakamura, supported by a Japanese naval force sent from Hainan, China, invaded Indochina. Men of the French colonial forces and the French Legion defended a Japanese attack on the town of Lang Son along the railway while diplomats continued to work out the terms. Lang Son fell under Japanese control by 24 Sep.
On 25 Sep, the French administration in Indochina officially turned over the territory to Japanese control, but fighting continued.
On 26 Sep, an amphibious landing was orchestrated at Dong Tac, a town south of Haiphong; by early afternoon, 4,500 Japanese troops and 12 tanks were outside the port city. Elsewhere, Japanese troops took control of the Gia Lam airfield near Hanoi and several rail yards. The fighting stopped in the evening of 26 Sep at the request of Emperor Showa. All land and sea routes to China were now severed.
Sources: American Caesar, Japanese Intelligence in World War II, the Pacific Campaign, Wikipedia.
Indochina Campaign Timeline
|20 Jun 1940||Vichy France opened northern Indochina to Japanese military mission and supporting troops.|
|1 Aug 1940||Japanese Foreign Minister Yosuke Matsuoka asked French Ambassador to Tokyo Arsène Henry whether Japanese troops might be allowed to enter Indochina to occupy certain airfields; Henry implied that his government would reject such a request. Meanwhile, Japanese Army aircraft were transferred from Northern China to Southern China.|
|7 Aug 1940||Lord Halifax of the United Kingdom and US Ambassador to Tokyo Joseph Grew voiced concerns over Japanese demands for French Indochina.|
|30 Aug 1940||French Ambassador to Tokyo Arsène Henry announced to the Japanese that the French government would allow 6,000 Japanese troops to station in Indochina and would allow the military use of ports, airfields, and railroads in the region. However, the French government attempted to delay on the implementation of the plan as long as they could.|
|4 Sep 1940||French Army General Maurice Martin took over Franco-Japanese negotiations for Indochina. Japanese intelligence intercepted a French cable that detailed Indochina affairs to the United States and the United Kingdom, signaling that the US and the UK still had influence in Indochina politics. Japanese Army argued that force must now to be used before US and UK openly asserted pressure.|
|5 Sep 1940||Japanese troops crossed the border into Indochina without French permission; French negotiator Maurice Martin suspended all talks in protest.|
|11 Sep 1940||Japanese Army Major General Issaku Nishihara reported to Tokyo, complaining that French authorities were delaying negotiations regarding Indochina matters.|
|14 Sep 1940||The Japanese Imperial General Headquarters gave the orders for troops to move into Indochina on 22 Sep 1940 regardless of the state of the Franco-Japanese negotiations. British intelligence intercepted this message, but it would not be deciphered until 20 Sep 1940.|
|17 Sep 1940||Franco-Japanese negotiations for Indochina re-opened; the Japanese increased their demands and openly threatened France with military action.|
|22 Sep 1940||France tentatively agreed to meet increased Japanese demands for Indochina.|
|23 Sep 1940||Japanese troops invaded Indochina despite French agreement to Japanese demands during negotiations on the previous day.|
|24 Sep 1940||Japanese troops occupied Lang Son, Indochina.|
|25 Sep 1940||France surrendered Indochina to Japan, but fighting continued.|
|26 Sep 1940||Japan conducted an amphibious landing at Dong Tac, Indochina; later that day, Japanese troops captured the Gia Lam airfield and several rail yards near Hanoi. In the evening, Emperor Showa ordered fighting to stop in Indochina since the French had already surrendered on the previous day.|
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James Forrestal, Secretary of the Navy, 23 Feb 1945