In 1520s, a man named David Ha-Reuveni traveled through Europe purporting to be the son of a Jewish king in a distant land who ruled over three of the ten lost tribes of Israel. Reuveni was received in European courts, and his grandiose plans sparked messianic fervor among Jews, as well as the conversos of Iberia and their children—children like Solomon Molcho, who became Reuveni’s most devoted follower. Joel Davidi Weisberger writes:
[Reuveni] first made his appearance in Venice in 1523, claiming to be the commander-in-chief of his father’s army, and requested aid from the local Jewish community. Although most regarded him with suspicion and even derision, he did gain a measure of support among notable members of the community who helped him gain an audience with the Pope Clement VII at Rome. His proposition was nothing short of astonishing: an alliance between the forces under his command and those of Western Christendom—in other words, a joint Jewish-Christian Crusade to liberate the Holy Land from Islamic rule.
[In] 1525 Reuveni was in Portugal where King John III received him as an official ambassador. Reuveni’s appearance in the city spread like wildfire and fired the imagination of Jews and Christians alike. Particularly smitten by him were the so-called marranos, those Jews who had been forced to live outwardly as Christians but secretly held on to their Jewish heritage. One of them, Diogo Pires, met Reuveni and asked to be circumcised. Reuveni, probably fearing for the success of his mission, dissuaded the young man.
But Pires circumcised himself and took on the Hebrew name Solomon Molcho. Reuveni, aghast at the young man’s audacity, urged him to flee the country, which he did. Most scholars agree that he studied Kabbalah for a time in Salonika, [then part of the Ottoman empire], under the tutelage of Rabbi Joseph Taitazak. There . . . Molcho gathered a group of devotees and it was there that he published his first book of sermons.
Molcho later returned to Christian Europe and, in 1532, was burned at the stake in Mantua. While the rabbinic scholar Yosef Shlomo Delmedigo of Crete and the German Jewish communal leader Josel of Rosheim remembered Molcho as a dangerous crank, the greatest halakhist and mystic of their day, Rabbi Joseph Caro—who may have met Molcho in Salonika—viewed him as an inspiration and a model of righteous martyrdom,
Read more on Jewish Link of New Jersey: https://www.jewishlinknj.com/features/34362-a-doomed-proposal-for-a-joint-jewish-christian-crusade-three-divergent-views-of-solomon-molcho