The special courts set up by the Catholic Church to check the spread of heretical opinion among the faithful, first formed in the 13th century. It was most active, however, in Spain, where it began in 1480. In time, the dreaded activities of this agency of the Church came to be directed mainly at ferreting out the Marranos, Jews who had been forcibly converted to Christianity and were found secretly observing the practices of Judaism.

It is estimated that in 350 years of Inquisition activities (roughly from 1480 to 1821), about 400,000 Jews were brought before these ecclesiastical tribunals; 30,000 were put to death. Punishment was carried out in public squares to serve both as a warning and a demonstration of “the glory of the Church.” Hence, an inquisitorial execution was known as auto-da-fe, an act of faith. Most notorious of the inquisitors was Thomas de Torquemada, who was largely responsible for the edict issued by Ferdinand and Isabella of Spain on the Ninth of Ab 1492, expelling all Jews from Spanish territory.