Mayadunne died in 1581 and was succeeded by Rajasinha.
In 1582, the new king invaded and conquered the kingdom of Kandy to the east, bringing the entirety of Sri Lanka into the Sitawakan fold, with the exception of the Jaffna Kingdom and Portuguese holdings in the south.
Karaliyadde Bandara, king of Kandy, fled to Trincomalee and subsequently died of smallpox; his young daughter, Kusumasana Devi, came under the protection of the Portuguese, who baptised her Dona Catherina and over the next decade claimed the throne of Kandy in her name.
Rajasinha's hold over the area was further disrupted by the rebellion of his viceroy Wirasundara Mudiyanse.
Though the uprising was crushed, and Wirasundara murdered, his son Konappu Bandara fled into Portuguese territory.
Baptised as Don Juan of Austria, he was to become an enduring opponent of the king of Sitawaka.


Portuguese intrigue in Rajasinha's court had dramatic results between 1583 and 1587; numerous nobles were executed following accusations of treachery.
Most importantly Rajasinha turned against the Buddhist clergy following the discovery of collaboration with his enemies; temples were destroyed, Sri Pada seized and given over to Hindu priests, and Rajasinha himself converted to Hinduism.
Many of the disaffected fled to the highlands.
 In Kotte, King Dharmapala formalised his donation of 1580 on 4 November 1583.

Rajasinha redoubled his efforts at dislodging Europeans and by 1587 he had amassed a force of some 50,000 infantry, as well as war elephants, cavalry, and a number of locally manufactured cannon.
The army commenced what was to become a twenty-two month siege of Colombo that year.
In the absence of a Sitawakan navy, the Portuguese—supplied from Goa via the sea—could hold out for extended periods of time.
A shift in policy by Calicut ensured that there was no hope of rekindling the old alliance with the south Indian kingdom, and Rajasinha was forced to abandon the siege in February 1588 to deal with unrest further inland.

The last years of Rajasinha's reign were spent defending the kingdom's borders, a task made more difficult by the Portuguese invasion of the northern Jaffna Kingdom in 1591.
The following year Portuguese forces briefly occupied Kandy, but were expelled.
Nonetheless a new, and formidable, enemy had emerged in the form of Konappu Bandara, who had returned to Kandy in the early 1590s.
Adopting the name Vimaladharmasuriya, he was seized the throne of Kandy, converted back to Buddhism, and married Don Catherina to legitimise his claim.
In 1593, he defeated Rajasinha at Balane and Mawela, effectively securing Kandy's independence from Sitawaka.
Rajasinha died the following year.

Despite the kingdom's impressive successes, much of its stability was dependent on a smooth succession and a competent ruler; Rajasimha's sudden death in 1593 (the same year the Portuguese appointed their first Governor-General of Ceylon) was met with neither of these and within less than a year Sitawaka had ceased to function as a cohesive polity.
Mayadunne died in 1581 and was succeeded by Rajasinha. In 1582, the new king invaded and conquered the kingdom of Kandy to the east, bringing the entirety of Sri Lanka into the Sitawakan fold, with the exception of the Jaffna Kingdom and Portuguese holdings in the south. Karaliyadde Bandara, king of Kandy, fled to Trincomalee and subsequently died of smallpox; his young daughter, Kusumasana Devi, came under the protection of the Portuguese, who baptised her Dona Catherina and over the next decade claimed the throne of Kandy in her name. Rajasinha's hold over the area was further disrupted by the rebellion of his viceroy Wirasundara Mudiyanse. Though the uprising was crushed, and Wirasundara murdered, his son Konappu Bandara fled into Portuguese territory. Baptised as Don Juan of Austria, he was to become an enduring opponent of the king of Sitawaka.

Portuguese intrigue in Rajasinha's court had dramatic results between 1583 and 1587; numerous nobles were executed following accusations of treachery. Most importantly Rajasinha turned against the Buddhist clergy following the discovery of collaboration with his enemies; temples were destroyed, Sri Pada seized and given over to Hindu priests, and Rajasinha himself converted to Hinduism. Many of the disaffected fled to the highlands.  In Kotte, King Dharmapala formalised his donation of 1580 on 4 November 1583. 
Rajasinha redoubled his efforts at dislodging Europeans and by 1587 he had amassed a force of some 50,000 infantry, as well as war elephants, cavalry, and a number of locally manufactured cannon. The army commenced what was to become a twenty-two month siege of Colombo that year. In the absence of a Sitawakan navy, the Portuguese—supplied from Goa via the sea—could hold out for extended periods of time. A shift in policy by Calicut ensured that there was no hope of rekindling the old alliance with the south Indian kingdom, and Rajasinha was forced to abandon the siege in February 1588 to deal with unrest further inland.
The last years of Rajasinha's reign were spent defending the kingdom's borders, a task made more difficult by the Portuguese invasion of the northern Jaffna Kingdom in 1591. The following year Portuguese forces briefly occupied Kandy, but were expelled. Nonetheless a new, and formidable, enemy had emerged in the form of Konappu Bandara, who had returned to Kandy in the early 1590s. Adopting the name Vimaladharmasuriya, he was seized the throne of Kandy, converted back to Buddhism, and married Don Catherina to legitimise his claim. In 1593, he defeated Rajasinha at Balane and Mawela, effectively securing Kandy's independence from Sitawaka. Rajasinha died the following year.
Despite the kingdom's impressive successes, much of its stability was dependent on a smooth succession and a competent ruler; Rajasimha's sudden death in 1593 (the same year the Portuguese appointed their first Governor-General of Ceylon) was met with neither of these and within less than a year Sitawaka had ceased to function as a cohesive polity.
Kingdom of Sitawaka