The Burmese-Siamese War of 1928-1929, also erroneously known as the 36th Siamese-Burmese War (see: National Mythmaking), was a conflict fought between the Kingdom of Siam and the Republic of Burma. The conflict's origins lay in Burma's quasi-civil war which broke out after the Burmese Revolt. In 1928 violent clashes broke out in Lower Burma between the forces of the Rangoon government and dissident Mon and Karen groups, resulting in the deaths of Siamese civilians in the disputed territories. After a year of fighting, Siam won a crushing victory.
Background
In centuries past, the Kingdoms of Burma and Siam had long had a tumultuous history with one another, lasting millennia. In nationalist pseudo-history, both sides bragged of the more than thirty wars waged between the two East Asian powers, although multiple different Burmese and Siamese dynasties had risen and fallen before any modern conception of a Burmese or Siamese nation had taken shape. This animosity had mostly ground to a halt after the British Empire began subjugating Burma in the Anglo-Burmese wars where parts of Lower Burma were placed under British control. What remained of the Burmese rump state by the mid-19th century had also repelled a Siamese invasion on its own in the Burmese–Siamese War of 1849–1855. This left hindered Siam's ability to pursue territorial claims on the border. Throughout the late 19th century, following Burma's ultimate subjugation under Britain, there were continuous disputes over the territory in the lower Tenasserim region, as well as in the Shan states, particularly over the Shan princedom of Mongpan. This also bled into other conflicts over Britain and Siam's border in Malaya, and over who controlled the local sultanates there. Though an Anglo-Siamese Border Commission was established in 1889, it failed to delineate a proper set of boundaries on the Burmese border until 1893, and even so, there were still reports of Siamese and British soldiers occasionally crossing the border of their respective frontiers. Ultimately, the situation remained tense, especially as France and Britain tried to pressure Siam to relent to western colonial land grabs on disputed border regions. Court intrigues escalated within the Kingdom of Siam, as various royal princes and local rural nobility competed over the positions of border commissioner, with some appointees favouring a more hands-off approach, whereas others tried to project Siamese hegemony on the frontier by force. After an abortive rebellion in the 1890s by the rural nobility, in part over questions of the border policy, the Siamese central government in Bangkok assumed greater responsibility for administration on the border. They thereafter chose to bide their time, confronting disputes judicially and diplomatically, as opposed to militarily.
This was well embodied by the Siamese policy during the Weltkrieg, even after Siam joined the Central Powers and declared war on Britain the border region remained relatively unharmed due to a mutual stalemate on account of a lack of troops and supplies. With Bangkok being able to reign in local nobles on the borders of the Kingdom, and Britain being unwilling to commit resources to a drawn-out conflict in the jungles and wilderness, a de-facto ceasefire held until the Peace with Honour was signed, barring some minor military incursions. Overall this helped breed resentment among the younger generation of the Siamese military, many of whom wished to make use of the opportunity to abrogate the Anglo-Siamese Border Commission and to seize disputed territories in Tenasserim and the Shan states by force.
This same hunger for conquest sprung up again in 1925 when Burma erupted into revolution much like the rest of India. Soon the Imperial British administration had all but collapsed with most British nationals and Anglo-Burmese collaborators evacuating to British India and Ceylon. As the Burmese declared their republic, hawks in the Siamese government and military proposed invading the fledgling country as part of the plan to extend Siamese hegemony further in the region. Ultimately cooler heads once again prevailed and Siam opted to recognise the Republic, lending it diplomatic recognition and limited material support on the condition that Burma would agree to honour the old treaties brokered by the Anglo-Siamese Border Commission. Negotiations were mediated by representatives of the Azad Hind, as well as diplomats from the Commune of France and the Empire of Japan, two of the first countries who had recognised the legitimacy of the Burmese Republic and who gave the negotiations international credence. Following the end of the British Civil War and the eventual recognition of the Union of Britain by Siam, the Syndicalists in Britain also lent their support to the treaty, formally ceding control over Burma and passing responsibility over the border to the newly decolonised Republic.
While Burma had been able to cast off the British yoke, tensions within had reached a breaking point and many of the nation's ethnic minorities erupted into an insurgency, most noticeably the Karen who had been favoured by the British and were now heavily persecuted under the new government for their supposed collaboration. For three years Burma tore itself apart in civil conflict, as the Tatmadaw and various Home Guards and Pocket Armies cut their teeth across the country. Indian 'advisers' became prominent and more or less directed the government in political, economic, and social affairs with many Indian units gaining valuable experience in aiding their Burmese counterparts. Across the border, the Siamese watched wearily with the sounds of gunfire and explosions rattling in the distance. Then in 1928, Karen rebels began making use of powerful ordinances and the Siamese began to mobilise their troops for conflict. Soon enough, disputed territories on the Kraburi River were shelled and officials from Siam claimed the small Siamese village of Ranong. Shortly after Siamese troops crossed the border and the 36th Siamese-Burma War had begun.
Burma In Flames
Tatmadaw troops in Lower Burma.
As Siamese troops began to pour across the border, the government began to rapidly mobilise its nascent army but it would soon find itself outmatched. The Tatmadaw, still young anhasng only fought against disparate rebel groups, would begin to disintegrate against better supplied and well-disciplined Royal Siamese Army led by Prince Baworadet the King's Cousins. Taking their place, many of the Home Guards and ethnic Pocket Armies took their place in the occupied territories, harassing the Siamese troops and inflicting devastating guerrilla attacks.
In Rangoon, the GCBA government pleaded with Indian diplomats to declare war on Siam but Calcutta refused, citing its alliance as strictly anti-British and no more. While much-needed arms, materials, and volunteer units were provided, the crucial involvement of Indian troops was denied and the anti-colonial alliance weakened. Early in the war, Siam made a series of powerful initial pushes into Burma, easily seizing the thin strip of land that connects the Lower Burmese region of Tenasserim to the rest of the country. Kawthaung fell shortly afterward. The Thais of Lower Burma sided with their eastern brothers, whilst most Mon and Karen initially favoured Siam, but quickly realised the invaders were little better than the government in Rangoon. The Mon tribes were treated fairly well considering their Buddhist faith and prior Siamese influence attempts, but Karen tribes were attacked by Siamese forces if they refused to collaborate, and several Christian Karen nationalists were persecuted. The city of Moulmein, the Tatmadaw’s last stronghold in Lower Burma, fell to Siamese as well, partly thanks to the aid from Mon tribes. The remaining Bamar and the anti-Siamese Karen turned to guerrilla warfare while the Homeguard militias expanded as many citizens began to arm themselves. The GCBA government signed truces with the radical Karen, Shan, and Rakhine nationalist groups to form a united front against the Siamese army.
Indian 'volunteers' in Burma.
The Siamese Northwestern Army led by Phraya Seriroengrit, pushed further into the Shan states and some Shan princes pledged their loyalty to the invaders, and unlike the Karen were treated well. Tensions between the Shan and the Karen in the Karenni States then escalated, with more and more Karen coming to the uneasy realisation that they needed to unite with the GCBA government against the invaders. Those Shan princes who refused to collaborate with Siam were either placed under house arrest or ousted from power. The remaining princes in the Upper Shan states, many of whom had been strong supporters of the Pegu Agreement, rallied their forces to resist the invaders. Through a combination of the Tatmadaw, the Princely armies, and guerillas in the Karenni states, the Phayap Army was temporarily halted at the northern part of the Salween River forcing the Phayap Army to slow down and consolidate its hold over the Lower Shan States.
Later in the year, the Siamese Navy was dispatched to reinforce the newly conquered territories in Lower Burma. Supplied by the ports of Moulmein and Kawthaung, it established a blockade around Rangoon to prevent support from Azad Hind from arriving and to stop the Burmese Republic from smuggling arms to the guerrillas in Lower Burma. This caught the attention of many Western businesses that had large investments in the Rangoon oil fields as well as Burma’s exports of rice, teak, and gems. Siam pledged to allow European and Americans through the blockade, but tensions soon escalated after a series of incidents wherein Western ships were nevertheless stopped and searched, or accused of arms smuggling. In one case the recently retired German Consul to Rangoon, Heinrich A.W. Huchting was briefly detained by Siam on his way home to Germany, causing an international embarrassment for the Siamese.
At the start of 1929 the “Federated Shan Territories” were re-established by the Siamese in the occupied Shan States. Siamese leadership argued for pushing even further into Burma, wishing to avenge the centuries of humiliation that their kingdom had endured at the hands of their neighbour, but to also secure the important strategic positions and valuable resources in the region. Another issue that could not be ignored was the growing rift between Prince Boworadet and Phraya Phibunsongkhram that was ever growing as both men had different ideas on how the war was going to proceed. This represented a microcosm of ongoing schisms within the Siamese military and the Royal court, where an older generation of officers led by Boworadet's "Royalists", competed with Phibunsongkhram's younger generation of "Modernists". Both leaders eventually came to an agreement and a major push was planned, intending to reach Mandalay and the Kachin Hills. Siam’s military began to build up the Western Army for this purpose, but the great push westwards failed to achieve the grand results the Siamese had been hoping for. The time that the Siamese High Command spent arguing strengthened the Burmese Defense on the west side of the Sittang River. Although many Siamese regiments managed to cross the Salween River, reaching as far as the Upper Shan States and the Karen Hills, the Tatmadaw and Homeguard guerrillas held the line and prevented the Siamese from reaching Mandalay and Rangoon. The Siamese began to overexert themselves with the war and unrest escalated in the recently annexed Laotian and Cambodian territories. The war soon began to wind down to a battle of endurance.
In the middle of the year, after observing several months of bloodshed and misery, Japan and Germany began to examine the possibility of helping end the war and jockeying for influence in rudderless Burma. Siam was haemorrhaging supplies, and manpower and draining the economy, whilst violence escalated within their country, potentially putting Japanese investments there at risk. The Burmese economy had been irreparably scarred by the loss of Lower Burma, the expenditure from the fighting, and the devastation of the countryside leading to a terrible harvest. The new German consul in Rangoon, Edwin O. Bloech managed to arrange for a conference to take place in Moulmein, that could end the war. Japan spied great benefits in having a pair of weak nations in Southeast Asia which may end up susceptible to new diplomatic and economic overtures. Germany meanwhile wanted to avoid a Siamese collapse into anarchy, as such an event would harm their investment in Asian markets, and violence in Laos and Cambodia could spill over into Cochinchina. Neither of the two empires wished to see the incredible wealth of Burma be razed to the ground by war and so Siam and Burma were forced to the negotiation table.
Negotiations In Moulmein
Negotiations began in Lower Burma and shortly after the Treaty of Moulmein was signed, ending the war. The terms of the treaty stipulated a conditional Burmese surrender and many humiliating conditions. Siam was allowed to annex the new Unified Former Thai Territories, as well as the districts of Möngmaü and Mehsakun in Mawkmai, of the southern Shan states as well as part of Kantarawadi in the Karenni states which were soon integrated into the Federated Shan Territories. Lower Burma, including the cities of Moulmein and Kawthaung, was placed under occupation, with no definitive agreement over what to do with them, besides some vague promises from the Japanese and the Germans about potentially holding a plebiscite, or splitting off the Thai portions of Kawthaung for Siam to annex. Overall, there was no easy way to dislodge the Siamese military from Lower Burma that wouldn’t endanger the peace treaty in its entirety. The Salween River became the new natural border between Burma and Siam. Despite initial opposition, the prominent opposition leader. U Ba Pe chose to support the peace treaty but clarified this was purely pragmatic until 'Burmese honour could be restored.