According to Josephus, a 1st-century Jewish Roman historian, Herod the Great fortified Masada between 37 and 31 BC as a refuge for himself in the event of a revolt. In 66 AD, at the beginning of the First Jewish-Roman War against the Roman Empire, a group of Jewish extremists, called the Sicarii, overcame the Roman garrison of Masada. After the destruction of the Second Temple in 70 AD, additional members of the Sicarii and numerous Jewish families fled Jerusalem and settled on the mountaintop, using it as a base for harassing the Romans.
In 72, the Roman governor of Iudaea Lucius Flavius Silva headed the Roman legion X Fretensis and laid siege to Masada. The Roman legion surrounded Masada, and built a circumvallation wall and then a siege embankment against the western face of the plateau, moving thousands of tons of stones and beaten earth to do so. Josephus does not record any attempts by the Sicarii to counterattack the besiegers during this process, a significant difference from his accounts of other sieges against Jewish fortresses. He did record their raid before the siege on Ein-Gedi, a nearby Jewish settlement, where the Sicarii allegedly killed 700 of its inhabitants.
According to Dan Gill, geological investigations in the early 1990s confirmed earlier observations that the 375-foot (114 m) high assault ramp consisted mostly of a natural spur of bedrock that required a ramp only 30 feet (9.1 m) high built atop it in order to reach the Masada defences. This discovery would diminish both the scope of the construction and of the conflict between the Sicarii and Romans, relative to the popular perspective in which the ramp was an epic feat of construction. The rampart was complete in the spring of 73, after probably two to three months of siege, allowing the Romans to finally breach the wall of the fortress with a battering ram on April 16. According to Josephus, when Roman troops entered the fortress, they discovered that its 960 inhabitants
