The Kalahom (Phya Sriworawong) had complete control over King Cetthathirat, and he could have disposed of him at any time. Before that, he had to deal with two other potential rivals in the race to kinghood: one was a brother of Song Tham, called Sri Sin, who was also serving as a monk. The other, of course, was Yamada Nagamasa. In a display of cunning skill, the Kalahom managed to pit the two men against each other by convincing Nagamasa that, in order to keep the promise made to Song Tham on his deathbed, Sri Sin had to be eliminated, since he was a potential usurper of the throne the late king wanted to reserve for Cetthathirat.
Nagamasa sprang into action, evicted Sri Sin from his temple, had him believe the Japanese guard would lead a rebellion with him, and ultimately, with the help of his Japanese platoon, exterminated the followers Sri Sin had gathered in the meantime. In the crucial battle, Nagamasa allegedly promised Sri Sin to pretend to charge against his army, only to suddenly make a 180-degree turn and join him to march on Ayutthaya. Sri Sin men were then mercilessly routed by Nagamasa’s soldiers.
This kind of treachery was commonplace in the days of the Japanese sengoku. Actually, from the exploits of the swordsman Miyamoto Musashi to the surprise attack on Pearl Harbor, Japanese military history is filled with similar events. Perhaps the most striking example comes from events that took place during the battle of Sekigahara in 1600. While the Eastern and Western armies were clashing on the plain, a few feudal lords waited on a hill with their men, trying to understand which side was prevailing. Once it was clear, they charged into the losing side, earning their share of the triumph.
Besides the rhetoric of chivalrous fighting, to Japanese soldiers until WWII, victory was the only glorious thing to earn on a battlefield, no matter by what means. Thus, while this betrayal of Sri Sin might be considered Nagamasa’s “stain” in a pristine career, one should be careful when judging his actions in these circumstances.
Resources: “Samurai of Ayutthaya – The Historical Landscape of
Early 17th Century Japan and Siam: Yamada Nagamasa
and the Way to Ayutthaya” by Cesare Polenghi (p. 53-54)
