When Woodrow Wilson, the President of the United States, declared war on Germany in April 1917, it was clear American entry would eventually turn the tide against the Central Powers (Germany, Austria-Hungary, the Ottoman Empire, and Bulgaria).
Watching on the sidelines, King Vajiravudh (Rama VI) considered his options. Siam had remained neutral since the outbreak of war in August 1914, and his nation enjoyed friendly relations with Germany, but Vajiravudh recognised the political value of throwing in his lot with the Allied Powers (Britain, France, Italy, and Japan).
He was convinced participation would be ‘…an excellent opportunity for us to gain equality with other nations.’ Siam had suffered from the imperial designs of the British and French, losing great swathes of territory in the 20 years or so prior to the outbreak of war in Europe.
Additionally, Siam had been coerced into signing agreements accepting the imposition of extraterritorial rights for the citizens of nations such as France, Britain, and the United States, and Vajiravudh hoped Siamese involvement in the war would lead to a revision of these unequal treaties.
Therefore, on 22 July 1917, despite the misgivings of some members of the government, King Vajiravudh instructed Interior Minister Chao Phraya Surasi to declare war on Germany and Austria-Hungary. Among the reasons cited was a claim the Central Powers were ‘ignoring the norms of warfare and fighting in an immoral way.’ One of Siam’s first acts was to intern, and later seize as war reparations, 12 ocean-going ships of the North German Line (NGL) as well as the Bangkok docks and warehouses of the firms Windsor Rose and Markwald.
There was a certain irony in Siam allying itself with France, a nation that had bullied her way into annexing large chunks of Siamese territory over the previous 50 years. Such are the vagaries of geo-politics.
Then again, Vajiravudh had been the first monarch educated abroad, being sent to Britain. He spoke fluent English, had been at Sandhurst Military College, and commissioned an officer in the Durham Light Infantry. The Anglophile monarch was contrasted by a number of royal relatives who had spent time being educated in Germany. A coup in March 1912 by 92 low-ranking royals, many pro-German, who hoped to replace Vajiravudh, did not pre-dispose the ruler towards Germany or her allies.
Not much happened until 21 September when the king gave the order for Chao Phraya Bodin, the Minister of War, to call for volunteers to make up an expeditionary force to fight in Europe. A limit was placed on overall numbers and an expeditionary force totalling 1,284 men was raised, under the overall command of Major General Phraya Pijaijarnrit (later promoted to Lieutenant-General and known as Phraya Devahastin). Volunteers were divided into three units: motor transport, medical, and aviation.
Thai records suggest the force left Siam on 19 June 1918 and landed at Marseilles on 30 July where the three sections were separated and sent for training in different parts of France. Yet a report sent to the American Consul in Melbourne, Australia on 4 June stated, ‘A contingent of Siamese troops has also joined the Allies.’ This is a strange discrepancy of almost two months between the Siamese chronicles and a contemporary account.
The motor transport section finally moved up to the Western Front in October 1918. For five days, from 26 October, the Siamese supplied French forces in an area subjected to German artillery fire and later received the Croix de Guerre from the French government as a unit citation.
About 95 air personnel, training at French Army Flying Schools, qualified as pilots, but had not completed their courses when the war ended on 11 November. The motor transport unit went into the occupied part of the Rhineland with French forces following the signing of the armistice.
There is a suggestion the medical unit included nurses, although no concrete evidence of this has come to light, at least in English or French. It is claimed these were the only women to serve in the trenches on the Western Front, but this seems extremely unlikely.
The aviation contingent returned to Siam, arriving in Bangkok on 1 May 1919 while the remainder of the volunteer force landed on 21 September.
A now almost-forgotten war memorial was erected in honour of the troops and stands on the edge of the Sanam Luang (Pramane) ground in Bangkok. Called the Volunteer Soldiers’ Monument it has inscribed the names of the 19 soldiers claimed as casualties of the conflict, none in battle. The remains of the casualties were interred in the monument on 24 September 1919 but the memorial itself was not officially unveiled until 22 July 1921, a strange and unexplained delay.
Of the 19 names inscribed on the monument, two men in Bangkok before the force left for Europe, presumably during training. Nine died in France and the other eight in Germany. Of these, 10 expired in hospitals or medical stations. Britain, Europe, and much of the rest of the world was gripped by Spanish influenza from the latter months of 1918 until 1920, one of the most virulent epidemics ever known. It is highly probable some of the hospital casualties were caused by Spanish flu. The remaining deaths appear to be the result of vehicular accidents.
Siam also participated in the Versailles Peace Conference with Articles 135, 136, and 137 devoted to her in the final Treaty of Versailles. In January 1920, Siam became a founding member of the League of Nations.
On 1 September 1920, King Vajiravudh’s decision to go to war was vindicated when the United States ceded her extraterritorial rights. France, after five years of extensive negotiations, relinquished her rights in February 1925 while Britain signed a treaty to the same effect in July the same year.