After the Roman victory over the Lusitanian hero Viriathus the settlement was named by the Romans, Occelum Durii or Ocellodurum (literally, "Eye of theDuero"). During Roman rule it was in the hands of the Vaccaei, and was incorporated into the Roman province of Hispania Tarraconensis. It was on the road from Emerita (modern Mérida) to Asturica Augusta (modern Astorga). (Ant. Itin.pp. 434, 439).
Two coins from the reign of the Visigothicking, Sisebuto, show that it was known at the time as "Semure".
During the period of Moorish rule the settlement became known by the names of "Semurah" or "Azemur". After the establishment of the Christian Kingdom of Asturias, the settlement became a strategic frontier post and was the scene of many fierce military engagements between the Muslims and Christians. Control of the town shifted between the two sides a number of times from the early eighth century to the late eleventh centuriy. During this period it became heavily fortified.
Henry IV granted Zamora the epithet of "most noble and most loyal city".
The most notable historic episode in Zamora was the assassination outside the city walls of the king Sancho II of Castile in 1072. Some decades before, kingFerdinand I of León had divided his kingdoms between his three sons. To his daughter, DoñaUrraca, he had bequeathed the "well fortified city of Zamora" (or "la bien cercada" in Spanish). All three sons warred among themselves, till the ultimate winner, Sancho, was left victorious. Zamora, under his sister who was allied with Leonese nobles, resisted. Sancho II of Castile, assisted by El Cid, lay siege to Zamora. King Sancho II was murdered by a duplicitous noble of Zamora, Bellido Dolfos, who tricked the king into a private meeting. After the death of Sancho, Castile reverted to his deposed brother Alfonso VI of León. The event was commemorated by the Portillo de la
