Oldest military and religious order in Spain.
It was founded in 1158 by two Cistercian monks who proclaimed a holy Crusade to defend the city of Calatrava against the Moor s. By the 15th century the order had 200,000 members and became increasingly involved in Castilian domestic politics. In 1489 it was incorporated into the crown by Ferdinand V and Isabella I , who deemed that all private armies had outserved their usefulness. It remained an honorary association of Spanish nobles until its dissolution in the 19th century.