Driven from that city, they went to Novi, but returned to Genoa in 1538, where Joseph practiced medicine for twelve years.

As for his brother Todros, he has tentatively been identified by Robert Bonfil with Ludovico Carretto, who is known to have converted from Judaism.

One of his chief concerns was also the release of the many Jewish captives taken by the vessels of the Italian republics and by the Corsairs; as in 1532, when Andrea Doria captured many Jews on taking Coron, Patras, and Zante; in 1535, when the emperor Charles V took Tunis; in 1542, when the galleys of Visconte Cicala [it] had imprisoned a number of Jews.

His major work, Dibre ha-Yamim le-Malke Zarfat we-'Otoman (Chronicles of the Kings of France and Turkey), is in the nature of a history of the world, in the form of annals, in which he represents the sequence of events as a conflict between Asia and Europe, between Islam and Christianity, the protagonist for Islam being the mighty Turkish empire, and for Christianity, France.

Having lived in Italy from his childhood and become acquainted with persons prominent politically, he is a valuable source for the history of his time; concerning many events, he had examined witnesses.

[2] The tenor of the book makes it an out-spoken representative of "the lachrymose conception of Jewish history" (Salo Baron).

Joseph ha-Kohen began the first version of this work in 1558, at Voltaggio, and concluded it, in its initial form, toward the end of 1563.

It circulated in Italy in manuscript and was edited for the first time by Samuel David Luzzatto and published in 1852 by Max Letteris.

From these, in 1557, he compiled his Matztib Gebulot 'Ammim (Who Setteth the Boundaries of Nations),[9] a history of the conquest of Mexico, to which he added a full account of the discoveries of Columbus.

He also compiled, in 1567, a book of polite formulas to be used in addressing letters, and a large number of verses, which are found, written in his own hand, at the end of his works.