The Great War or World War I began in 1914 between the Central Powers, which included Germany, Austria-Hungary, Bulgaria, and Turkey, and the Allied Powers, which included Britain, France, Belgium, Russia, and other nations. The war lasted for four years.
Thailand, under the reign of King Vajiravudh, maintained its neutrality until 22 July 1917 when the King led the country into war, joining the Allied Powers. King Rama VI ordered a group of defence diplomats led by Major General Phraya Phichai Charnyarit (Phad Thepahatsadin Na Ayudhaya) to contact the entente in Europe. The diplomats left Thailand on 11 January 1917.
The Thai government recruited volunteers to form an Expeditionary Force. After training, a troop of 1,284 soldiers sailed from the shores of Thailand on 20 June 1918 and arrived in Marseilles, France in August. The Expeditionary Force fought until the end of the war, when the Allied Powers won, and the Peace Conference was signed on 11 November 1918. The Thai troop marched in victory alongside the Allied troops at the Arc de Triomphe in Paris; in London, England, and in Brussels, Belgium.
The volunteers arrived back home on 21 September 1919, and the troop marched in front of the King. The 19 soldiers who fell during the campaign were cremated in Europe, and had their ashes brought back to their homeland to be honoured. To commemorate their service, King Vajiravudh ordered a memorial built in the shape of a stupa to hold the ashes. On 24 September 1919, the King officially dedicated the memorial and ordered a march of honour for the fallen heroes. The monument became known as the World War I Volunteer Memorial, and the commemoration day is 11 November of every year.