During his rule, the Spanish troops mutinied and Spain went bankrupt. He was rather moderate in comparison to Alba, requesting Philip to grant a general amnesty to all, with the exception of persistent heretics, and to permit the emigration of those who would not comply. Grand things, but this did not achieve much with Philip.
His early career was that of a government official and diplomat. In 1563 he gained the king's confidence as his representative at Rome. In 1568 he was appointed lieutenant-general to Don Juan de Austria during the suppression of the Morisco revolt in Granada, and he also accompanied Don John during the Lepanto campaign, his function being to watch and control his nominal commander-in-chief, whose excitable temperament was distrusted by the king.
Philip must have been satisfied with Requesens, for he named him viceroy in Milan, a post usually given to a great noble. Requesens was only a gentleman of cloak and sword (caballero de capa y espada), though by the kings favour he was grand commander of the military order of Santiago in Castile. He was credited with having shown moderation at Milan, but it is certain that he came into sharp collision with the archbishop, Saint Charles Borromeo, who took up the cause of his flock.
His docility rather than his capacity marked him out to succeed Alba. The king wished to pursue a more conciliatory policy, without, however, yielding any one of the points in dispute between himself and the revolting Dutch. Requesens came to Brussels on November 17, 1573, and till his death on 5 March 1576 was plunged into insuperable difficulties. With an empty treasury and unpaid mutinous troops, no power on the planet could have helped Requesens to succeed. He was an honest official who was worn out while trying to do the impossible.