Sigismund, who entered Prague in the summer of 1436, hired Hunyadi and his 50 lancers for three months in October 1437 for 1,250 gold florins, implying that Hunyadi had accompanied him to Bohemia. Hunyadi seems to have studied the Hussites' tactics on this occasion, because he later applied its featuring elements, including the use of wagons as a mobile fortress. On 9 December 1437 Sigismund died; his son-in-law, Albert was elected King of Hungary in nine days. According to historians Teke and Engel, Hunyadi soon returned to the southern frontiers of the kingdom which had been subject to Ottoman raids. In contrast with them, Mureşanu says that Hunyadi served King Albert in Bohemia for at least a year, till the end of 1438.