Ananda Pyissi and Yanda Pyissi was deployed at a fort at Ngasaunggyan. Invasion (1283–1285) Battle of Ngasaunggyan (1283) The invasion began on 22 September 1283. Prince Sangqudar was the commander-in-chief of the invasion force; his deputies were Vice Governor Taipn, and commander Yagan Tegin. The Mongol armies marched to the border in two columns. One column advanced along the Taping River using over 200 boats; the other proceeded by land and joined the first column at the Burmese fort at Ngasaunggyan. The Burmese chronicles report an overwhelming number of Mongol forces laying siege to the fort although their numbers are greatly exaggerated. (The chronicles say that the Burmese army numbered 400,000 men while the Mongol army numbered 20 million men and 6 million horses.) The Burmese withstood the siege for over two months but the fort fell on 3 December 1283. Invasion of northern Burma The defeat at Ngasaunggyan broke the back of Burmese defenses. The Burmese army lost several thousand men as well as senior commanders. Kaungsin, the next fort in line, fell just six days later on 9 December 1283. The Mongol sources say that the Burmese lost 10,000 men at Kaungsin. The Mongol armies pushed farther south into the Irrawaddy valley. They took the ancient Burmese capital of Tagaung, about 380 km north of Pagan on 5 February 1284. There, the invaders paused their advance. They "found the heat of the searing Irrawaddy valley excessive", and evacuated Tagaung, allowing the Burmese to return to Tagaung on 10 May 1284. But the Mongol army renewed their offensive in the following dry season. They retook Tagaung, and defeated another Burmese stand south of Tagaung, probably near Hanlin, on 26 January 1285, opening the way to Pagan, about 270 km south. After the defeat, the king panicked, and fled to Lower Burma. The evacuation proved premature. The Mongol forces did not advance on Pagan as it was not part of their invasion plan. The country fell into chaos. In Lower Burma, the king found himself isolated, let alone plan a counterattack. Although the king's three sons ruled the nearby regions (Bassein (Pathein), Prome (Pyay), and Dala-Twante), the king did not trust any of them, and he and his court settled at Hlegya, west of Prome. Without the full support of his sons, the presence of the king and his small army impressed no one. A usurper named Wareru seized the