Joseph Nasi was born as a Secret Jew in Portugal in 1524, long after all Jews had been expelled. He escaped Portugal by following his paternal aunt, Beatrice de Luna (Gracia Mendes), when she went from Lisbon to Antwerp in 1537. After studying at the University of Louvain, he entered the banking establishment of Mendes and was responsible for settling the family's affairs when Gracia left in 1545 for Italy.
He was very popular among the highest nobility in the Netherlands. Despite that, he had to flee in 1547. The following years he spent in France, where he became known to King Francis I, and later in Italy. Early in 1554 he joined his aunt, Gracia Nasi, in Constantinople, where he was circumcised and assumed the name of Joseph Nasi. In August he married her daughter Reyna. This cemented his economic and political fortunes with her. In 1556 he joined her in organizing the blockade of the port of Ancona to avenge the persecution of the Secret Jews there.
Joseph Nasi made a series of incredibly fortunate political decisions. In the struggle for the succession to the Ottoman thrown between Selim and Bajazet, Joseph Nasi supported the former, with the result that he received many favors from him, including a high rank in the Ottoman court. Due to his intimate knowledge of European affairs and statesmen, and his chain of agents throughout the Western world, he exercised great influence on the foreign policy of the Ottomans, taking a prominent part in the peace negotiations between Poland and Turkey in 1562.
In 1569 he encouraged the Netherlands to revolt against Spain and a letter of his, promising Turkish support, was read out at a meeting of the Calvinist consistory of Amsterdam. By then his influence at Constantinople had grown, due to the accession to the throne of his friend Sultan Selim II, who esteemed him as his favorite.
Immediately after this, he was granted a monopoly on the import of wines through the Bosporus, said to have brought him a net income of 15,000 ducats annually. In addition, he obtained important trading privileges in Poland.
In 1568, in order to satisfy certain claims against the king of France (who had stolen the family property left in that country because Jews were not permitted in France), Joseph Nasi obtained the sultan's authority to confiscate one-third of the merchandise on French ships docking at Alexandria. The French envoy, Grandchamp, launched an elaborate plot with Nasi's former physician, Daoud, in the hope of disgracing him. The plot failed and Daoud was excommunicated by the principal Jewish communities of the Turkish Empire.
Soon after Selim's accession, he appointed Nasi duke of the island of Naxos and the adjacent archipelago, whose Christian duke had recently been deposed, and eventually he also became count of Andros. He administered his duchy mainly from his palace at Belvedere near Constantinople.
During the War of Lepanto (1570–71) Nasi's dominions were re-conquered by the Venetians for the former duke, but Nasi's authority was soon reinstated.
Joseph Nasi is best known for his attempts with his aunt to establish an independent Jewish community in Tiberius. As early as 1558 or 1559, Gracia Mendes had obtained from the sultan various concessions in Tiberius. The city on Lake Kinneret was mostly ruins. She planned to found a yeshivah there. In 1561 Joseph obtained confirmation and extension of this grant, giving him ruling authority in Tiberias and seven nearby villages in consideration of an annual payment.
In the winter of 1564–65 the rebuilding of the ruined walls of Tiberius was completed, ensuring a certain degree of physical security. This was the only practical attempt to establish some sort of Jewish political center in Palestine between the fourth and 19th centuries.
Joseph Nasi then tried to give Tiberius an economic foundation by investing there in both the wool and silk industries. Several hundred families settled there. He then sent a circular letter to the Jewish communities of Italy inviting them to move to Tiberius, offering them stipends. Numerous families excitedly prepared to move.
Unfortunately, Turkey and Venice went to war. The Tiberias Plan failed.
Sources: Gates to Jewish Heritage