Analysis of information sources in references of the Wikipedia article "Mông Cổ xâm lược châu Âu" in Vietnamese language version.
In A.D. 1232 an army of 30,000 Mongol warriors invaded the Chinese city of Kai-fung-fu, where the Chinese fought back with fire arrows...Mongol leaders learned from their enemies and found ways to make fire arrows even more deadly as their invasion spread toward Europe. On Christmas Day 1241 Mongol troops used fire arrows to capture the city of Buda in Hungary, and in 1258 to capture the city of Baghdad in what's now Iraq.
The country lost about half its population, the incidence ranging from 60 percent in the Alföld (100 percent in parts of it) to 20 percent in Transdanubia; only parts of Transylvania and the northwest came off fairly lightly.
