One hundred years ago, on 28 June 1919, Prince Chraroonsakdi Kritakara and Prince Traidos Prabandh Devakula put their signatures to the Treaty of Versailles which formally ended the state of war between the Allied Powers and Germany. Siam had entered World War I or the Great War rather late, three years after its outbreak in Europe. When Siam declared war on Germany and Austria-Hungary on Sunday, 22 July 1917, by royal proclamation, many foreign diplomats, not least the Germans, were caught by surprise, given the cordial political, military and economic relations the Kingdom of Siam had enjoyed with the German Empire before August 1914. Therefore, the Siamese entry into the war needs explanation. Stefan Hell's magnificent study tells in full detail how neutral Siam became involved in a European war on the side of those European colonial powers who had forced the Southeast Asian kingdom to relinquish large parts of its territory only two decades earlier.

In the first part of his meticulously researched and lavishly illustrated book the author explores Siam's relationships with the major Western powers before and at the outbreak of the war. Though at the beginning of the nineteenth century British influence in Siam was dominant in almost all fields, the Germans had secured a strong position in the country. In fact, Siamese–German trade had boomed in the two decades following King Chulalongkorn's first visit to Europe (in 1897). It is estimated that by the eve of World War I up to one-third of Siam's foreign trade was with Germany. In 1900, 45 per cent of all ships calling or arriving at Siamese ports were sailing under the German flag, compared to only 38 per cent sailing under the British flag. The British, in particular, were most concerned about a ‘peaceful takeover’ of Siam by the German Reich. As Hell emphasises, ‘Germany enjoyed a high standing among the Siamese elite as being the home of advanced technology, quality consumer goods and machineries, and as a beacon of discipline and military achievement’ (p. 34). Germans actively participated in the implementation of King Chulalongkorn's modernisation scheme. Of the 207 foreigners working in the service of the Siamese government by 1904, 34 were Germans, most of whom were employed in the development of the postal and telegraph services and in the construction of the Siamese railways. They were only outnumbered by British nationals, who made up almost one-half of all foreign advisers and experts.

When the Great War broke out in Europe, the Siamese elite decided to stay out of the conflict. To a great degree this neutrality was enforced by the conflicting views of the main actors on the political stage besides King Vajiravudh — who had studied in Britain and did not make a secret of his personal sympathies. Whereas the British-educated Princes Charoon and Devawongse, as well as the pro-Russian Prince Chakrabongse, were leaning towards the Allied Powers, two other princes — namely Paribatra and Mahidol — were in favour of the Central Powers. Hell provides rare bibliographical information on these key policymakers. He shows how the pro-German forces among the Siamese elite, led by Prince Paribatra and Prince Mahidol, who had received their military training at the Imperial Military School in Berlin-Lichterfelde, were increasingly forced into the defensive. Persistent rumours throughout 1915 and 1916 about an imminent German-backed coup aimed at ousting the King and replacing him by Prince Paribatra further contributed to the isolation of the pro-German camp (p. 43). After the United States joined the Allied forces in April 1917, the debate among members of the Siamese elite intensified as to whether or not Siam should also declare war on Germany and the other Central Powers. The pro-Allied faction, led by Prince Chakrabongse, received the support of the King himself who, under a pseudonym, published a series of articles explaining the moral reasons for Siam entering the war. Outrage over the unrestricted German submarine warfare targeting civilian vessels grew even stronger with the death of two Siamese citizens in one of the submarine attacks.

Immediately after the declaration of war the Siamese government took swift action. In a dawn swoop, well-prepared long beforehand, all male Germans, Austrians and Hungarians were arrested by the Siamese government and put into a detention camp. A few days later, women and children followed their husbands and fathers. A total of 296 persons, including 43 women and 58 children, were detained. Among the internees were the famous Luis Weiler, director of the Siamese National Railway (northern line), and Dr Oscar Frankfurter, a highly respected scholar who had served the Siamese government for more than thirty years, latterly as the director of the National Library. As a retaliatory measure the German government arrested eight Siamese who were studying in Germany at that time. After the closure of the German embassy in Bangkok, the embassy of the Netherlands took over the safeguarding of German and Austrian-Hungarian interests in Siam.

Hell discusses in considerable detail in Part II the overall good treatment of the detained Germans and Austrian-Hungarians in Siamese hands (before being sent to India) and the fate of the Siamese students interned in a northern German officer camp. Some details are hardly known and have so far not been disclosed elsewhere, such as the fate of Prince Nikorn Davan Devakula, the 19-year-old son of foreign minister Prince Devawongse, who had been sent to Russia for military training and was captured by German troops in January 1918 during the German conquest of the Crimea. When the Germans had learned of Prince Nikorn's status they proposed to the Siamese government shortly before the end of the war to exchange him for the release of Oscar Frankfurter and the family of Wilhelm Brehmer, a successful businessman in Bangkok (p. 131).

The second half of Siam and World War I describes the mobilisation of Siamese volunteers who followed the call which the Minister of War had issued on 22 September 1917. ‘Mainly army reservists volunteered to join, as well as policemen, members of the Wild Tiger Corps, and civil servants and civilians without military experience. However, after the initial enthusiasm the mood shifted for some reasons and a number of volunteers requested and received permission to leave’ (p. 143). In the end only some 1,300 Siamese volunteers of the Siamese Expeditionary Force (SEF) were sent to France where they arrived in late July 1918. At that time the final ‘Allied Hundred Days Offensive’ beginning with the Battle of Amiens was already under way, and when the first Siamese contingent arrived on the battlefield in September, the Germans were already in retreat behind the Hindenburg Line. Fortunately, none of the 19 deaths among the SEF occurred on the battlefield, as the majority died of pneumonia resulting from the influenza pandemic which claimed more than 400,000 lives in France alone (p. 186).

Far from restricting himself to the purely technical aspects of the military training the Siamese volunteers received in France, Stefan Hell also discusses the cultural dimension of the Franco–Siamese cooperation, especially the racist attitude and rude behaviour of French officers towards the Siamese soldiers. Though the SEF did not receive its baptism of fire on the battlefield, it was to gain some experience as an occupying force after the armistice of 11 November 1918. In mid-December a regiment of several hundred Siamese soldiers arrived at the small German town of Neustadt in the Palatinate region where they would stay for several months.

More significant than the real contribution of the SEF on the West European battlefield was its symbolic value, all the more so since Siam's decision to enter the war had come at a moment ‘when the situation in Europe was not absolutely rosy for the Allies’, as Prince Charoon sharply remarked (p. 90). I agree with Hell's opinion that by sending troops to Europe, regardless of their actual fighting capacities, Siam was signalling to the Allied Powers its willingness to share the burden of war and at the same time its demand to be treated henceforth as an equal partner in the international arena. Or to put it in the author's own apt words: ‘The most significant outcome of joining the war was that Siam won the war’ (p. 284). The renouncement of the unequal treaty that Siam had concluded with Germany was one essential outcome of the Treaty of Versailles, paving the way for the rescindment of unequal treaties with the United States, Britain, France and all other Western countries during the 1920s.

Stefan Hell's excellent study of Siam's involvement in World War I is a fine piece of scholarship providing new perspectives on an often neglected chapter of modern Thai history. It also makes accessible less-known primary sources from the French, British, German and Austrian Archives. Besides, the author brings to light documents from the Thai National Archives, thanks to the efforts of Thai historian Bhawan Ruangsilp whose contribution to this wonderful project is explicitly acknowledged. Stefan Hell's book is superb not only with regard to its wealth of detail and analytical depth, its careful integration of numerous historical photographs, postcards, pamphlets — almost on every page — makes the reading a particular pleasure. The volume is highly recommended to anyone interested in Thailand's connection with the world in the twentieth century.