An Overview of Thailand's Participation in WW2

by Ally Diwik

In December 1941, over the course of only a few days, the Thai government moved from a public stance of neutrality to a military alliance with Japan. Thailand’s alliance with Japan would ultimately define Thailand’s role in World War II in the Pacific Theater. ​

(continued) After allying itself with Japan, Thailand would go on to declare war against the British and Americans as well as assist the Japanese in supplying their troops through the completion of the infamous Thailand-Burma Railway. Thus, it is valuable to examine how this rapid shift in government policy took place in Thailand. 

​Prior to the outbreak of war in the Pacific, Thailand was a quasi-independent state in which the British and French exercised considerable influence. The area to the east of the Menam Chao Phraya Basin fell within the French sphere of influence while the area to the west of the river basin lay within the British sphere. However, in December 1938, Phibunsongkhram took power in Thailand as a military dictator. Phibunsongkhram, also known as Phibun, maintained friendly relations between Thailand and Japan. Relations with Japan had been increasing amiable since the early 1930s and when paired with Thailand’s new strongly nationalistic policies which were anti-Chinese at home and pro-Japanese abroad, relations between Thailand and European powers were increasingly strained. Thai-European relations continued to falter when in November 1940, Phibun ordered the invasion of French territories in western Laos and northwestern Cambodia that had formerly been under Thai control. This move on the part of Thailand was strongly supported by Japan. 

The relationship between Thailand and Japan didn't remain friendly especially when it came to the convenience of Thailand. Japanese aggression in the Pacific increasingly strained the Thai-Japanese relationship. Thai officials, including Phibun himself, repeatedly appealed to the British and Americans to help Thailand defend its territory and sovereignty against Imperial Japan. But neither country was able to offer any significant support to the Thai government. As a result, as relations between Japan and its Pacific rivals worsened following the advance of Japanese forces into southern French Indo-China, Phibun declared that Thailand would remain neutral. Unfortunately, the likelihood of war only increased in the following months which in turn increased apprehension within the Thai government that they would be able to remain neutral. 

Phibun attempted to remain friendly and yet noncommittal towards the Japanese officials that urgently lobbied his government for support. But by December 8th, 1941, the Thai government was forced to seriously consider all options following the Japanese attack on Pearl Harbor and the impending Japanese invasion of Thailand. Four main options were discussed at a cabinet meeting on December 8th. The options included were: (1) Japan and Thailand would conclude an offensive/defensive alliance; (2) Thailand would join the Tripartite Pact with Germany, Italy, and Japan; (3) Thailand would cooperate with Japanese military operations; (4) Thailand and Japan would undertake the mutual defense of Thailand. All four options held the expectation that Japanese forces would be allowed to pass through Thailand. Additionally, each option was accompanied by the Japanese offer to assist Thailand in recovering its lost territories. On the evening of December 8th, 1941, the Japanese ambassador, accompanied by military and naval attachés, went to see Phibun. They arrived with a draft of an alliance treaty they expected the Thai government to agree to. On December 21st, the formal signing of the Treaty of Alliance took place as scheduled at Wat Phra Kaeo. Phibun then reshuffled his cabinet to ensure that it represented a more pro-Japanese group of officials. Then, on January 25th, 1942, the deputy foreign minister announced over the radio that Thailand was joining Japan and declaring war on Britain and the United States. 

Following the declaration of war, the most significant role Thailand played in the Pacific War was in building the Thailand-Burma Railway. The Japanese decided it was necessary to build a railway to connect Bangkok, Thailand, with Moulmein, Burma. By early 1942, shipping lanes had become incredibly vulnerable to allied attacks and thus a railway was necessary to bring much-needed supplies to Japanese forces in Burma. It was designed to be 259 miles long running through jungles, across rivers, and over the mountain chain that separated Burma and Thailand. To build the railway, the Japanese and Thai used thousands of Allied prisoners of war (POWs) as well as hundreds of thousands of Romusha (indigenous contract laborers) from Burma, Malaya, Java, and other conquered nations as a labor force. Construction began in October 1942 and within a few months the Imperial General Command in Tokyo, anxious to complete the project, moved up the completion date to October 1943. This acceleration was known as “the Speedo” and it was during this time that the Thailand-Burma railway earned its nickname: the “death” railway.

Ultimately, during World War II, Thailand was only able to gain minor territorial concessions in Burma, Malaya, Laos, and Cambodia as a result of its alliance with Japan. Additionally, the Thai economy greatly suffered during this time which undermined public support for Phibun. The waning public support for Phibun allowed resistance groups based in the United States and Britain to make contact with similar groups within Thailand. The Free Thai, as these groups were known, conducted raids against the Japanese and ultimately succeeded in infiltrating the Thai government. By July 1944, Phibun was forced to resign and his 1942 declaration of war was determined to be unconstitutional and therefore legally void. As a result, Thailand never needed to official surrendered to the allies. Instead, following Phibun’s resignation, Thailand did its best to repair diplomatic relations with the Allies and ceased the majority of its wartime operations. 

References:

1. Eldredge, Sears, “The Thailand-Burma Railway: An Overview” (2014). Book Chapters. Book 21. http://digitalcommons.macalester.edu/thdabooks/21. 
2. Keyes, Charles F. and Jane E. Keyes. “Thailand.” Encyclopaedia Brittanica, Encycloaedia Brittanica, Inc., 9 June 2019, https://www.britannica.com/place/Thailand/Chulalongkorn-and-the-foundations-of-modern-Thailand. 
3. Swan, William L. "Thai-Japanese Relations at the Start of the Pacific War: New Insight into a Controversial Period." Journal of Southeast Asian Studies, vol. 18, no. 2, 1987, pp. 270-293.
4. Wilson, Hugh. "The Best of Friends: Britain, America and Thailand, 1945-48." Canadian Journal of History, vol. 25, no. 1, 1990, pp. 61-84.

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