Task: Question Generation
Input (English): Passage: According to the Yuan dynasty chronicle and Marco Polo's accounts, a Burmese army "invaded" the Mongol territory of Gold Teeth, and was defeated by the Mongol army in April 1277. The battle took place either at the Vochang valley  or 110 km southwest at Kanngai , which the Burmese called Ngasaunggyan. The Yuan Chronicle reports that only 700 men defeated a Burmese army of 40,000 to 50,000 with 10,000 horses and 800 elephants. It also reports only one Mongol was killed, in trying to catch an elephant. According to Marco Polo, the Mongol army consisted of 12,000 mounted archers, and the Burmese army numbered 60,000 men with 2000 elephants, "on each of which was set a tower of timber, well-framed and strong, and carrying from 12 to 16 well-armed fighting men." Even then, the 40,000 to 60,000 figures of the Burmese army strength were likely eye estimates and may still be too high; the Mongols may have erred "on the side of generosity" not to "diminish their glory in defeating superior numbers." According to Marco Polo's account, in the early stages of the battle, the Turkish and Mongol horsemen "took such fright at the sight of the elephants that they would not be got to face the foe, but always swerved and turned back," while the Burmese forces pressed on. But the Mongol commander Huthukh did not panic; he ordered his troops to dismount, and from the cover of the nearby treeline, aim their bows directly at the advancing elephants. The Mongol archers' arrows threw the animals into such pain that they fled.
Output (English): What document said that a Burmese army invaded Gold Teeth?