The king was unfazed. He ordered Thado Minsaw, the ruler of Ava, to take care of the northern states while he personally led the Lan Xang campaign. On 1 October 1574, Thado Minsaw's army (6000 men, 800 horses, 80 elephants), made up of regiments from Upper Burma and the Shan states, marched north. Six days later, Bayinnaung's four armies (34,000 men, 1800 horses, 180 elephants), with regiments from Lower Burma, Lan Na and Siam, began the Lan Xang campaign. The armies arrived before Vientiane after 60 days marching. On 6 December 1574, the king and his massive armies faced no opposition entering Vientiane, as Soulintha had already evacuated to the countryside. Fortunately for the Burmese king, Soulintha was viewed as a usurper by his own officers, who arrested him and presented him to the conqueror. Burmese armies again fanned out to and received tribute from the Lao countryside, including easternmost Lan Xang, which is now part of present-day Vietnam. The Burmese king appointed a younger brother of Setthathirath, Maha Oupahat (Chao Tha Heua), king of Lan Xang with the regnal name Voravongsa I, and returned to Pegu on 16 April 1575. Since he was a true high Lan Xang royal he was accepted by the populace as the rightful successor to Setthathirath. Lan Xang was finally under control.