With much of western mainland Southeast Asia under his control, Bayinnaung now felt ready to take on Siam. He needed an overwhelming advantage in manpower over Siam because unlike interior Shan states, Siam could not be overwhelmed by the strength of his Portuguese firearms alone. Siam was a prosperous coastal power in its own right, and its forces included Portuguese firearms, ships and mercenaries. On 16 July 1563, he sent an embassy to Siam, demanding one of the four white elephants in possession of the Siamese king as tribute. As expected, King Maha Chakkraphat duly refused. On 1 November 1563, five armies (60,000 men, 2400 horses and 360 elephants) left Pegu to start the campaign. Another army from Lan Na was supposed to come down but King Mekuti of Lan Na had revolted.