In March 1241, the Tatar-Mongols under the Khan Batu overwhelmed the mountain defenses and entered through the Verecke Pass (separating the county of Bereg from Galicia) to plunder Transylvania and the Kingdom of Hungary. They destroyed many towns and monasteries, killing up to half the population. Hungarian villages, being mostly in the valleys, bore the greatest brunt of the slaughter, and this helped start the decline in Hungarian population that influenced the modern political disposition of the territory. The Mongols destroyed the towns of Teceu (Técső then) and Ocna Slatina (Aknaszlatina then) as well as the surrounding villages. In 1242, they hastily retreated, after learning that the Great Khan had died, in order to back their leader Batu to become the new Great Khan.