Manuel, King of Portugal, had begun his reign favourable towards the Jewish population, releasing all the Jews who had been held captive under his precedecessor John II. However, his attempts to marry the Infante Isabella of Aragon (heiress to the united crowns of Spain) depended on conformity to the anti-Jewish policy already followed by Spanish monarchs Ferdinand and Isabella. As a result, he decreed that all Jews must convert to Christianity or be expelled from Portugal.
Editors. "Expulsion of Jews from Portugal". The Literary Encyclopedia. First published 01 March 2010
[http://www.litencyc.com/php/stopics.php?rec=true&UID=1340, accessed 20 September 2014.]