By the third century Palmyrans had begun to assert their independence partly due to general instability in the Roman Empire, posed by the proximity to the Sassanians who by now controlled their important trade depot at the mouths of the Tigris and Euphrates rivers. In the mid third century as Roman emperor Valerian was captured and killed by the Sassanians a local leader Septimiuis Odenathus rose to prominence in Palmyra challenging the might of the Sassanians. But Odenathus was also murdered in 267AD and his wife the infamous Zenobia came to power ruling on behalf of her son. She had expansionist ambitions of her own (it is rumored she murdered her husband) and took control of the cities of Bosra and began looking to Antioch and Egypt by which time Emperor Aurelian had had enough and in 272AD defeated her in battle in Homs, and took her back to Rome as a prisoner. He left behind a garrison in Palmyra but before long a local insurrection overpowered the garrison at which point Aurelian returned and gave his troops free rein to attack, massacre and pillage the city and its inhabitants. From then on Roman power was complete - under the Byzantines churches were added to the city but in 634 Palmyra fell to the great Arab warrior Khaled ibn Walid and although the city was fortified by the Arabs, it never again reached such prominence.