Complex sentence: Sakya Pandita preached sermons along his way and arrived at Prince Godan's camp in 1247 in Lanzhou in the current province of Gansu, where the Mongol troops were exterminating Chinese by throwing them in a river.
Split into simpler sentences: Sakya Pandita preached sermons along his way and arrived at Prince Godan's camp in Lanzhou, in the current province of Gansu, in 1247. There the Mongol troops were exterminating Chinese by throwing them in a river.