The Kingdom of Siam, as Thailand was known at the time, was one of the small states that joined the First World War on the side of the Allied powers. Siam joined the war in mid-1917 after having remained neutral for three years. Domestically this led to interning enemy aliens and requisitioning enemy businesses and property; internationally it meant severing diplomatic ties with Germany and Austria-Hungary. Being at war could have implied simply programmatic speeches and limited economic support to the Allied war efforts, but Siam went beyond such limited engagement when it decided to assemble an expeditionary force and participate actively in the war in Europe.

Siam’s governing elite used military means to achieve strategic political goals both domestically and internationally. These efforts were by and large successful. Siam managed to elevate its international reputation and gain respect as a civilised member of the community of states, thereby gradually emerging from the limitations imposed upon it by imperialist powers. The elite strengthened the prevailing social structure by displaying power and sponsoring patriotism.

This article will first give some basic information about Siam and its international relations in 1914, before describing the three years of Siam’s neutrality from the outbreak of war to 1917. It then aims to contextualize Siam’s declaration of war of 1917 before summarising the war’s impact in Siam and Siam’s war in Europe, with a focus on the expeditionary force in France and Germany.

No detailed historiographical study on Siam’s participation in World War I exists to date, but some studies touch on the war in other contexts,[1] and one intriguing article extrapolates information about the expeditionary force from inscriptions on the war memorial in Bangkok.[2] Primary documents from all relevant governments are rich and accessible, however, and an in-depth study based on Thai, German, French and British primary sources by Stefan Hell and Bhawan Ruangsilp will be published to coincide with the centenary of Siam’s declaration of war in 2017.

Siam in 1914

In 1914 Siam faced a number of challenges. Internationally, its sovereignty was not secure. While it had never been formally colonised, its existence in a period of imperialism depended to a large part on the policies of its colonialist neighbours, Britain and France. It had been forced to concede territory to them only a few years earlier and was limited in its foreign trade and domestic jurisdiction over foreigners by unequal treaties.[3]

Siam was an absolute monarchy ruled by Vajiravudh, King of Siam (1881-1925), who had adopted the dynastic name Rama VI. Buddhist religious practice and education were deeply interwoven with the kingdom’s feudal structure. Society was predominantly agrarian, with the capital Bangkok the only urban centre. Industrial development was in its infancy and much of the commercial activity was in the hands of Chinese immigrants who had moved to Siam in large numbers in the previous decades.

The British-educated Vajiravudh had ascended the throne in 1910, after the long and transformative reign of his father, Chulalongkorn, King of Siam (1853-1910). Vajiravudh, with his artistic sensibility and shyness in public, struggled with the bureaucratic demands of governing the country. He did not enjoy the great popular support his father had received, and had already faced a serious challenge to his rule in an averted plot attempt originating among junior army officers in 1912.[4]

The Siamese state had been undergoing an extensive administrative reform process, during which it adopted many elements of Western administrative culture in order to strengthen central rule over the kingdom and make the government more effective. The state employed Western technical advisers and developed a legal system along Western lines. This reform process was driven by two distinct groups: by the king’s uncles, cousins and brothers, some of whom had been involved in the reform since the previous reign; and, increasingly, by an emerging civilian bureaucracy. The West was the focal point for the ruling royal and civilian elite; it epitomised modernity and civilisation in statesmanship, military, law, technology, aesthetics, arts, fashion, education and commerce.[5]

Siam’s economy during this period was dominated by rice production. Its only other marketable commodities were teak, sugar, rubber and tin. The manufacturing and financial industries were still in their infancy. Aided by the development of infrastructure and decreasing transport costs during the first decades of the 20th century, the Thai rice industry was integrated into the regional economy in Southeast Asia and southern China, exporting nearly one-third of its total production. Siam was the third-largest rice exporter after British Burma and French Indochina. Rice production and exports grew slowly but steadily during this period, as did the economy as a whole; Siam’s imports were limited primarily to construction materials, machinery and consumer goods. Hampered by limitations in the unequal treaties to the duties that could be levied on imports, a quarter of state revenue came from the licensed sale of opium during this period. The First World War initially disrupted foreign trade when shipping routes between Siam and Europe were blocked, but then led Siam’s exports to grow in the non-European markets, primarily in trade with Japan and the United States. The First World War had a significant negative impact on Siam’s public finances and economy by causing a sharp increase in global silver prices, making the material value of Siamese coins higher than their face value. This led people to hoard and melt down coins to sell the silver abroad. In 1919-1920 things came to a head when economic mismanagement and the lack of capital were aggravated by a disastrous rice crop. In the following years, Siam found itself in both a financial and an economic crisis. The government even banned rice exports during 1920, in spite of peaking international demand, in order to ensure domestic supply. Public accounts remained in deficit until the end of the reign.[6]

Bangkok had a sizeable community of Western diplomats and businessmen. The British were dominant, but others, including the French, Germans, Dutch, Danish, Portuguese, Austrians, Russians, Americans, and the notable non-Western exception, the Japanese, all vied for political and economic influence in mining, timber, shipping and trading, and infrastructure development.

Siam did not view Germany as a colonial power in Southeast Asia. Germany was therefore perceived markedly differently from Siam’s imperialist neighbours, Britain, France and the Netherlands. German trading firms successfully set up shop in Bangkok, and German shipping lines soon dominated passenger and cargo transport between Bangkok and the two major trading hubs, Singapore and Hong Kong. German shipping lines so dominated the transport between these ports that when war broke out in 1914 and German ships were no longer available, Siam’s foreign trade collapsed for a period of several weeks before ships from other countries filled the gap.

In Siam, German technology was considered cutting-edge. For the advanced technology of the time – the railway and the telegraph – Siam used German firms, engineers, equipment and technological standards. The same can be said for German medicine which was imported from Germany, much like other advanced technology. Siam had been employing German technology and expertise for the administrative and technological development of the country. German and American influence among the large group of foreign advisers and competing foreign interests in Siam served to counterbalance that of France and Great Britain.

The Phase of Neutrality, 1914-1917

There was no argument over policy in Bangkok when war broke out in Europe and the government issued a royal proclamation on 6 August 1914 for the observance of neutrality. It was a prudent decision to stay out of the conflict; Siam had no stake in it and the trajectory of the war was impossible to foresee. However, during the following three years between mid-1914 and mid-1917, the position of neutrality became increasingly difficult to uphold. The war forced Siam’s officials increasingly to take sides in everyday matters involving Germans, Britons or French. Relations between the enemy representatives in Siam became increasingly antagonistic, and both sides stepped up their lobbying efforts to convince Siam to join their camp. Moreover, news of German actions on the battlegrounds of Europe in a war of unprecedented mass killing and industrial and chemical warfare gradually pushed those with a neutral stance into the Allied camp.

Bangkok became a propaganda battleground during the years of Thai neutrality. The prize was an important strategic alliance and commercial benefits in the only market in the Far East not yet colonised. Moreover, nine ocean-going German commercial vessels had sought refuge in Siam’s neutral waters, anchored behind the sand bar at Paknam and thus safe from enemy war ships.

Among the elite in Siam, attitudes were certainly mixed: some, like King Vajiravudh and his foreign minister, Prince Devawongse Varopakarn (1858-1923), while not concealing their sympathies for Britain, preferred maintaining neutrality. Some favoured siding with the Allies; the highest military officer in the country and key military adviser to the king, Prince Chakrabongse Bhuvanadh (1883-1920), and Siam’s minister in Paris and key foreign affairs adviser to the king, Prince Charoonsakdi Kritakara (1875-1928) both favoured joining the Allies. Yet other policymakers and influential princes had studied in Germany and developed strong personal links and therefore held pronounced pro-German sentiments. These included Prince Paribatra Sukhumbandh (1881-1944), Prince Mahidol Adulyadej (1892-1929) and Prince Rangsit Prayurasakdi (1885-1951).

During the first months of 1917 the pro-British advocates of entering into the war started to gain the upper hand over those favouring neutrality and those with pro-German leanings. After three years of neutrality, Siam fundamentally altered its policy in mid-1917 and entered the world war on the side of the Allied powers. King Vajiravudh was the main agent of this decision. He decided to follow the “young Siamese”, as he called them, choosing a more assertive policy rather than following the old guard.

The reasons behind Bangkok’s decision to declare war were complex. Clearly, the world war was the single most important event at the time and entering into the war boosted Siam’s stature. Indeed, putting Siam at war against a strong European power like Germany was unprecedented in Thai history and sent a strong signal of the power and stature of the king himself. Domestically, this provided a focal point for the elite around which to rally society and instil patriotic sentiments, similar to sponsoring a navy league or creating a paramilitary organisation. Declaring war also had immediate material benefits, as Germans were pushed out of the economy and German companies, property and ships were requisitioned.

Strategically, the declaration of war served Siam’s central political aims: to regain full sovereignty as an equal member of the international community in a new post-war order by dissolving unequal treaties, and to become a respected partner in a post-war international system. Moreover, after three years of intense warfare in Europe, a conviction had set in that Germany might not be able to end the war with a military victory. Therefore, it required little political capital to join the Allies in mid-1917 in the face of news received in Bangkok during the past three years of German war atrocities like its indiscriminate use of chemical weapons and sinking of foreign passenger ships. When the United States assumed a position of moral leadership by entering the Allied camp in April 1917 and rallied neutral states like Siam to follow its lead, Siam used the opportunity to portray itself as a modern and civilised state.

Declaring war on Germany also meant giving in to mounting Allied pressure to do so. It allowed Britain to strengthen its already dominant position in commerce by taking over those sectors hitherto dominated by Germans. These included shipping, as well as the development of public infrastructure, mainly in the railway sector. The Allies were relieved to see Germans removed from government service and public life in Siam, as it curbed German spying and subversive actions. Siam’s declaration of war on Germany thus eliminated a political and economic competitor in Siam and reinforced Britain’s dominance.[7]

Siam at War, 1917-19

The Effects of the War in Siam

Siam declared war on Germany and Austria-Hungary on 22 July 1917. The immediate effect of this declaration was local. In a well-prepared and well-executed operation, all German and Austro-Hungarian nationals in the kingdom – some 320 men, women and children – were put under guard at daybreak. Over the course of the day, all men who were not diplomatic staff were assembled and interned without bloodshed. The German ships anchored on the Chao Phraya were seized before their German crews could cause irreparable damage; all German-owned businesses, shops and restaurants were locked up; and all German property and assets were confiscated. British businesses rejoiced that their German competitors had been put out of business over night.

The nine steam ships were the main prize for the Siamese government. Allied diplomats in Bangkok had pressured the government for some time to capture the ships and hand them over to them so they could use them for international trade to and from Bangkok. The government pondered what to do with the ships for several months and then decided to award the largest seven ships to the Allies, retaining the remaining two.

193 German and Austro-Hungarian men of military age were interned at a prisoner-of-war camp set up at a military hospital in central Bangkok. 124 German women and children were interned at the German Club, including the Thai wives of German men and their children. Conditions at the camps were generally good. The camps were clean, inmates received necessary medical care and sufficient food, and the general atmosphere between prisoners and guards was amicable. These good conditions allowed the government to project the civilised image it desired. During the following months the government, however, became increasingly uneasy about the existence of two internment camps in the capital. It also began to receive a constant stream of complaints from the prisoners. The British minister exerted strong pressure on the government to accept London’s offer to ship the prisoners to an internment camp in India, as it doubted Siam’s ability to keep the Germans locked up effectively and to prevent them from sabotaging British interests. In the end, much to the dismay of the Germans, the king agreed. The Germans and Austrians were deported to India in February 1918, where they were interned at the prisoner-of war camps in Ahmednagar and Belgaum until their repatriation to Germany in 1920.

German Reactions to the Declaration of War

The international effects of the declaration of war were predictable, with Siam receiving much praise from the Allied camp. All of mainland Southeast Asia was now free of Germans who could spy upon or sabotage Allied interests. The Allies had been particularly concerned about subversive German activities supporting independence movements in British India and French Indochina.

Meanwhile, the German government was caught wrong-footed. The foreign ministry in Berlin struggled over what to make of its newest enemy. Both German officials and the press soon began to downplay the significance of Siam’s entry into the war, describing it as a militarily insignificant reaction to British pressure. Some German voices did, however, point to the economic impact Siam’s decision would have in a post-war world in which Germany could no longer use Siam as a foothold in Southeast Asia.

When Siam declared war on Germany, nine Siamese students were in Germany; Thai diplomats had failed to bring them to safety in Denmark and Switzerland in time. In early August 1917, they were imprisoned in Berlin and later transferred to Celle Castle, a prisoner-of-war camp for enemy officers and prominent civilian prisoners.

The students were assigned a spacious room in the castle with electricity and heating and were furnished by the Siamese legations in France and Copenhagen with food, clothing and daily necessities. Since they also received plenty of cash through the Danish Red Cross, they were able to purchase anything they were lacking. The students paid a French officer to cook and clean for them, rented a piano, and continued their studies at a camp university founded by the inmates. The comfortable life notwithstanding, one of the students passed away in Germany in late October 1918.

On 20 November, the remaining Siamese were sent with several hundred other prisoners of war by train to the Dutch border and onwards to Belgium. From there they made their way to Paris and volunteered to serve as interpreters for the Siamese expeditionary force.[8]

The Siamese Expeditionary Force

Siam’s decision to declare war was a shrewd political move, but there were precedents from other non-European small states. The decision to send an expeditionary force to Europe, however, was radical. It was designed to demonstrate both Siam’s modernity and civilisation to the West and the seriousness with which Siam’s king and elite viewed the need to uphold the principles of international law and morality. It was further designed to strengthen Siam’s claim to equal treatment in a post-war settlement.

The decision likely evolved from a suggestion by the French government that a volunteer ambulance unit be set up by Siamese students in Europe. French diplomats further suggested that Siam could provide automobile drivers to assist in supplying the troops and aviators, who could be trained at French flying schools as pilots and mechanics.

Siam’s army in 1917 was not particularly well-equipped or well-trained for participation in the slaughter of World War One. It possessed little modern equipment or artillery and had no experience of operating in Europe or in a climate or terrain other than its own. It did, however, possess officers trained in modern warfare and military strategy and, importantly, it had a modern flying squadron. No other arm of the military was considered as modern as the air force. The king and his senior diplomats and military officers gladly picked up on the French suggestion.[9]

That the army of a sovereign East Asian nation should fight in Europe was unprecedented and electrifying for the elite and large parts of the general population in Bangkok. Opposition to the decision to become actively involved in the war was limited. Some opponents were politically motivated, as was true of the pro-German members of the elite; opposition also came from religious groups who argued more fundamentally against the involvement of Buddhists in war.

Opposition notwithstanding, the minister of war issued a call for volunteers in September 1917 to form a contingent to display the Siamese National Flag in Europe. He spelled out three objectives: to actively aid the Allies; to gain active military experience; and to uphold national dignity, honour and glory. The assembled expeditionary force consisted of a 414-men-strong aviation corps of pilots and aircraft mechanics and an 870-men-strong motor corps of automobile drivers, mechanics, medical and support staff.

While the troops were being assembled, trained and receiving smallpox vaccinations, an advance mission led by Major-General Phraya Bijai Janriddhi (1877-1951), commander of the expeditionary force, travelled to Europe in January 1918 to make preparations for the troops’ arrival. Phraya Bijai had spent several years in Belgium and France, where he had received military training; he spoke French and understood French military culture. In Europe, George V, King of Great Britain (1865-1936) and French President Georges Clemenceau (1841-1929) received him and his fellow-officers; they visited the front and made arrangements for the troops in Marseilles and elsewhere.

Months passed with preparations and training in Siam. Once suitable transportation was secured, nearly 1,230 officers and enlisted men boarded the S.S. Empire for Europe on 20 June. They were given a grand send-off by the king and senior princes and by cheering crowds along the banks of the Chao Phraya River. Via Singapore, Colombo and Port Said the S.S. Empire sailed safely to Marseilles, where she arrived five weeks later on 30 July 1918. While the send-off had been festive, the welcome was rather unceremonious. Although the central purpose of the expeditionary force was to display Siam’s military ability and its pride as a sovereign kingdom, French officials briefly mistook the troops for Indochinese troops, to the horror of Siam’s diplomats and senior officers assembled in Marseille. Moreover, the Siamese contingent arrived at a time when some ten thousand American soldiers were arriving in France every day, further diminishing the attention they received from their hosts.

After disembarking, the aviation corps was transferred to training camps at Istres, Avord and Pau, while the transport corps was transferred to a camp at Lyon, where the troops received basic training. After two months in camp, in October 1918 the motor corps was moved to the vicinity of Chalons in the Champagne region behind the front and began supplying troops using French trucks.

Tensions between the Siamese troops and their French liaison officers had been building during the weeks in camp, but under combat conditions they came to a head. The language barrier was a problem; while both the Siamese and the French had recruited as many suitable interpreters as possible, it remained a challenge to communicate effectively with the French officers under battlefield conditions. More importantly, the French army was ill prepared to integrate the Siamese troops into on-going military operations, largely due to the condescending and racist attitudes prevalent among the French liaison officers. They increasingly abandoned their assigned roles as advisers and began ordering the Siamese troops directly, sidelining the Siamese commanders. The effect of French behaviour on the morale of the troops was disastrous, upsetting the senior Siamese officers, diplomats in Paris, high-ranking military and civilian officials in Bangkok, and even the king himself. When confronted with Siamese accusations, officials at the French foreign ministry understood the danger the situation posed to their goals of having the Siamese troops in France: namely, improving political and commercial relations with Indochina’s neighbour. The situation deteriorated so much that the king and his senior advisers contemplated aborting the mission.

However, on 11 November the armistice was signed and fighting ceased, removing much of the pressure from the situation. It was in reaction to these tensions that the French foreign ministry triggered the military command to order the Siamese motor corps to cross into German territory behind their own troops. The Siamese occupation of Germany was thus not the result of a tactical military decision but of a political effort to appease the upset ally. The decision greatly pleased all involved, from the military commanders in Europe to the king in Bangkok himself. In the end, the Siamese were willing to put the animosities behind them and focus on reaping the political benefits from the tremendous effort of deploying troops to Europe.

King Vajiravudh went so far as to describe the day his troops entered German territory as the proudest day of his life. These extraordinary events served the king’s ambition to fashion himself as a soldier-king and comrade of the troops. He also wished to use Siam’s participation in the war as a vehicle to strengthen national unity and patriotism, with the soldier-king standing at the centre of both the nation and the war effort.

The main contingent of the motor corps stayed in the German region of the Palatinate from December 1918 until July 1919, operating primarily in the area around Neustadt. Before embarking for their return journey, Siamese troops participated in the victory parades the Allies organised in Paris, London and Brussels. These parades in July of 1919 were highly symbolic opportunities to visually demonstrate Siam’s presence in the capitals of the great European powers under the eyes of kings and presidents. Siam had affirmed its presence among the victorious states that had fought to uphold international law, justice and civilisation and had defeated brute force and aggression.

In total, nineteen members of the Siamese expeditionary force lost their lives; half of them fell victim to the influenza pandemic, while the remaining deaths resulted from accidents. None of the Siamese troops died from enemy fire or other battle-related injuries.

The expeditionary force returned to Bangkok in two batches. The 400 officers and men of the aviation corps left France without having been to the front and arrived in Siam in May 1919. The motor corps returned to Bangkok in September. For this occasion the government organised the official peace celebrations in which the entire capital and the provincial centres throughout the kingdom seem to have participated. At the end of four days of festivities and religious ceremonies, the ashes of the fallen soldiers were enshrined in a memorial built at a central location close to the Grand Palace and the ministry of war.[10]


The events described here centred around two crucial decisions. The first was to declare war in July 1917; the second was to send troops to Europe, which meant actually going to war. Going to war became a focal point for elite-driven nationalism and a reaffirmation of royal power. By sending Siamese troops to fight abroad, the kingdom signalled its existence to the West as a partner willing to share the burden of war and demanding equal treatment and respect.

The most significant outcome of joining the war was that Siam won the war. It renounced its unequal treaty with Germany and dictated the terms of peace as a junior partner alongside the Western Allies in the Treaty of Versailles. The United States, and in the following years Great Britain and France, rescinded their unequal treaties and Siam regained sovereignty over its trade and public finances. By the 1930s, the last remnants of extraterritorial jurisdiction had been abandoned.[11]

The second most significant impact of joining the war was Siam’s greatly enhanced role internationally, as it became a founding member of the League of Nations. Over the following two decades, Siam gained knowledge and technical assistance for the development of a variety of sectors through its League membership. The war also led to the modernisation of the Siamese army, acting as a catalyst for the development of the military and especially of the aviation division. Siam now possessed trained pilots, mechanics, drivers, and officers with a first-hand understanding of modern warfare.[12]

In their efforts to regain sovereignty and to enhance Siam’s international stature, policymakers skillfully leveraged the kingdom’s active participation in the war to demand equal treatment from France and Britain. Moreover, in domestic affairs Siam’s victorious emergence from the war gave elite-driven nationalism a strong boost. This was, however, then overshadowed by the financial and economic difficulties that beset the kingdom during the final years of King Vajiravudh’s reign.

Although Siam was a minor participant in the Great War, its participation was a decisive event in Siam’s/Thailand’s international history. Siam’s participation in the war had no major military significance and France’s suggestion to send troops to Europe was as much politically motivated as was Siam’s decision to do so. Siam’s political gains from participating in the war, however, were remarkable. They influenced not only the remaining years of the absolute monarchy, but also events after the coup d’état of 1932 in foreign relations and social and economic development.

Stefan Hell, Independent Scholar

Section Editor: James P. Daughton