In 1520, Photisarath came to the throne and moved the capital from Luang Prabang to Vientiane to avoid a Burmese invasion. Setthathirat became king in 1548, after his father was killed, and ordered the construction of what would become the symbol of Laos, That Luang. Setthathirat disappeared in the mountains on his way back from a military expedition into Cambodia and Lan Xang began to rapidly decline. It was not until 1637, when Sourigna Vongsa ascended the throne, that Lan Xang would further expand its frontiers. His reign is often regarded as Laos's golden age. When he died, leaving Lan Xang without an heir, the kingdom divided into three principalities. Between 1763 and 1769, Burmese armies overran northern Laos and annexed Luang Phrabang, while Champasak eventually came under Siamese suzerainty.