invasion of 1765–1766). While the main Burmese armies were massed at the Siamese border, a rebellion broke out in Manipur. Characteristically, Hsinbyushin did not recall the armies. Instead, he led an expeditionary force to put down the rebellion in December 1764. Having arrived back at Ava in April 1765, the Burmese king then sent 10,000 men to reinforce the southern army, which now numbered 30,000. The Burmese army now had mobilized 50,000 men. (This likely represented the largest mobilization of the Burmese army since Bayinnaung's 1568–1569 invasion.). The Burmese artillery corps were led by a group of about 200 French soldiers who were captured in the Battle of Syriam in 1756 during the Burmese civil war of 1752–1757. Siamese preparations The Siamese too had been busy planning their defenses since Hsinbyushin accession. Their defenses had been on alert since they got the Tavoy governor to revolt in mid-1764. King Ekkathat had already launched a massive mobilization drive across the entire country when Maha Nawrahta came down with his army and retook Tavoy in November 1764. In all, the Siamese southern defenses alone comprised over 60,000 troops. Ekkathat placed several of "his best legions" along the entire western arc from the Three Pagodas Pass to Kanchanaburi across Tavoy, to the Gulf of Siam in the extreme south to face off Maha Nawrahta. In the north, the main Siamese defensive line began at Sukhothai and Phitsanulok. The defenses farther north immediately facing the northern Burmese army relied on small forts built by local chiefs. Finally, the Siamese relied on a heavily fortified Ayutthaya city, strategically sited at the estuary of two rivers where high rising waters in the rainy season had kept it safe against enemies over the centuries. The Siamese had used their wealth to acquire several thousand muskets and artillery. Some of the cannon were long, and fired 100 lb (45 kg) balls. (When the Burmese finally captured Ayutthaya in 1767, they found over 10,000 new muskets and ammunition in the royal armory, still unused even after a 14-month siege.). As was the case in 1760, foreign mercenaries (including some Europeans and the Chinese) were hired for Ayutthaya's defense. At least one English ship was enlisted for her broadsides. Burmese battle plan The Burmese battle plan was greatly shaped by their experience in the 1759–1760 war. First, they would avoid a single pronged attack route along the narrow Gulf of