The Toungoo command selected Prome as their next target. In March 1551, Bayinnaung's army (9000 troops, 300 horses, 25 elephants) attacked the city. But the city's musket and artillery fire kept them at bay for over three months. He retreated on 19 June 1551, and regrouped with men from central Burma (up to Myede and Sagu) whose rulers now submitted to the new rising power. Another 9000-strong army resumed the siege on 21 August 1551, and took the city on 30 August 1551. Bayinnaung ordered the execution of Prome's ruler Thado Dhamma Yaza I but regretted the decision immediately afterwards. He appointed his second eldest younger brother as viceroy of Prome with the style of Thado Dhamma Yaza II.