Analysis of information sources in references of the Wikipedia article "Battle of Mohi" in English language version.
(along, it seems, with explosive charges of gunpowder) on the massed Hungarians trapped within their defensive ring of wagons. King Béla escaped, though 70,000 Hungarians died in the massacre that resulted—a slaughter that extended over several days of the retreat from Mohi.
1 9 The Mongols are known to have used gunpowder and firearms in Europe as early as 1241 at the Battle of Mohi in Hungary. See Jacques Gernet, A History of Chinese Civilisation (Cambridge University Press, 1982). page 379
After defeating the Kipchak Turks (Cumans), Bulgars and Russians, the Mongol army under Subutai took Cracow and Breslau, and on 9 April 1241, defeated a German army under Duke Henry of Silesia at Liegnitz. The Mongols under Batu defeated the Hungarians under King Bela IV at Mohi on the Sajo on 11th April, 1241. ... it has priority over the use of gunpowder, which the Mongols used two days later in the battle beside the Sajo. ...
superior mobility and combination of shock and missile tactics again won the day. As the battle developed, the Mongols broke up western cavalry charges, and placed a heavy fire of flaming arrows and naphtha fire-bombs
33 D'Ohsson's European account of these events credits the Mongols with using catapults and ballistae only in the battle of Mohi, but several Chinese sources speak of p'ao and "fire-catapults" as present. The Meng Wu Er Shih Chi states, for instance, that the Mongols attacked with the p'ao for five days before taking the city of Strigonie, to which many Hungarians had fled: "On the sixth day the city was taken. The powerful soldiers threw the Huo Kuan Vets (fire-pot) and rushed into the city, crying and shouting.34 Whether or not Batu actually used explosive powder on the Sayo, only twelve years later Mangu was requesting "naphtha-shooters" in large numbers for his invasion of Persia, according to Yule
The Mongols probably had a nominal force of at least 30,000 men, with the personal units of Batu and Sube'etei forming the core of the army.