A possible cause for the revolt was the decision of Emperor Hadrian to build a pagan temple to Jupiter in Jerusalem. Simon Bar Kokhba started the revolt and inflicted massive casualties on the Romans. The war ended when the Roman army — including "Fretensis" and Danubian troops under the command of Sextus Julius Severus — reconquered the entire territory and successfully besieged the last Jewish stronghold, the fortress of Betar. Legio X Fretensis sustained heavy casualties in the course of the revolt.