The Order of Alcántara guarded the Leonese frontier of the Reconquista. It began as the Order of San Julián del Pereiro and took its lasting name when Calatrava handed it the town of Alcántara on the Tagus. A Cistercian daughter-order of Calatrava, it became one of the three great orders whose masterships the Spanish crown absorbed.
The Order of Alcántara was León’s answer to Calatrava — a Cistercian military order raised to defend the western frontier of the Reconquista. Under Calatrava’s tutelage it grew from a small brotherhood at a Leonese hermitage into a great territorial order of Extremadura.
Its green cross became one of the three that dominated the Spanish orders, alongside the red sword-cross of Santiago and the red cross of Calatrava.
The order arose around 1176 as the Order of San Julián del Pereiro, a knightly brotherhood on the Leonese frontier, confirmed by the pope the following year. It was affiliated to Calatrava, which held rights of visitation over it.
In 1218 Calatrava, unable to garrison the newly won town of Alcántara on the Tagus, ceded it to the Leonese knights. They moved their headquarters there and took the name by which they have been known ever since.
Alcántara’s knights held a chain of castles across Extremadura and pressed the frontier southward, sharing in the great advances of the 13th century that carried Christian arms toward the Guadiana and beyond.
Like its sister-orders it combined the monastic rule of the Cistercians with the life of a frontier garrison, its commanderies both convents and fortresses.
The mastership of Alcántara, like those of Santiago and Calatrava, became entangled in Castilian politics and coveted by the crown. Its last independent master, Juan de Zúñiga, resigned his office as the Catholic Monarchs gathered the orders in.
From 1494 the crown administered the order, and in 1523 its mastership was permanently annexed to the Spanish crown along with the others.
Alcántara left its green cross across the towns and castles of Extremadura and a great convent by the Roman bridge that gave the order its name. Its estates, folded into the crown, added to the resources of a unifying Spain.
With Santiago and Calatrava it completed the trio of Castilian–Leonese orders that carried the Reconquista to its end.