The ambitious Bayinnaung had built an empire too large to govern.

His son and successor Nanda Bayin, upon coming to the throne of Toungoo in 1581, had been faced with a rebellion of his uncle, the viceroy of Ava, whom he had defeated three years later.

Lacking neither energy nor initiative, Nanda Bayin in December 1584 marches into Siam, which had been a vassal of his father, to subjugate the Siamese patriot Naresuan.

Nanda Bayin has sent several armies into the Chao Phraya river valley over the past three years.

Naresuan, in a series of brilliant military operations, has defeated three Burmese armies that had invaded Siam, frustrated repeated attempts of the Burmese to capture the capital, and simultaneously defeated Cambodian invasions.

Nanda Bayin has continued to attempt to crush Tai independence, launching further offensives in 1586 and 1587, despite the bloodshed, misery, and resources exhausted by continual warfare.

Naresuan is again able to withstand the Burmese onslaught.

Naresuan, attacking the Cambodians in 1587, drives to the walls of Lovek, the capital, before a lack of supplies forces an end to the campaign.