The army also used scorched earth tactics as a means to intimidate the enemy and to secure easier future victories. The ruthless sacks of Martaban in 1541 and Prome in 1542 served to secure the fealty of Lower Burma to the upstart regime of Tabinshwehti of Toungoo. Threatened by Bayinnaung's army of a sack of their capital Ayutthaya, the Siamese duly surrendered in 1564. When the Siamese changed their mind in 1568, the city was brutally sacked in 1569. Two hundred years later, the army's brutal sack of Pegu in 1757 secured the subsequent tribute missions of Chiang Mai, Martaban and Tavoy to Alaungpaya's court. Indeed, the brutal 1767 sack of Ayutthaya has been in a major sore point in the Burmese-Thai relations to the present day.