] 17th- to mid-20th-century theories

Since at least the 17th century both Jews and Christians have proposed theories concerning the lost tribes, based to varying degrees on Biblical accounts. An Ashkenazi Jewish tradition speaks of the Lost Tribes as Die Roite Yiddelech, "The little red Jews", cut off from the rest of Jewry by the legendary river Sambation "whose foaming waters raise high up into the sky a wall of fire and smoke that is impossible to pass through".[2]
On December 23, 1649, after Manasseh ben Israel, a noted rabbi of Amsterdam had been told by Antonio de Montezinos that some of the Lost Tribes were living among the Native Americans of the Andes in South America, he wrote:
“ ... I think that the Ten Tribes live not only there ... but also in other lands scattered everywhere; these never did come back to the Second Temple and they keep till this day still the Jewish Religion ... [3]
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In 1655, Manasseh ben Israel petitioned Oliver Cromwell to allow the Jews to return to England. Since 1290, Jews had been prohibited by law from living in England. One of the reasons for Cromwell's alleged interest in the return of the Jews to England was the abundance at the time of theories relating to the end of the world. Many of these ideas were fixed upon the year 1666 and the Fifth Monarchy Men who were looking for the return of Jesus as the Messiah who would establish a final kingdom to rule the physical world for a thousand years. They supported Cromwell's Republic in the expectation that it was a preparation for the fifth monarchy - that is, the monarchy which should succeed the Assyrian, the Persian, the Greek, and Roman world empires.
Mixed in with all of this was a background of general belief that the Lost Ten Tribes did not represent ethnic Jews who partially formed the ancient Kingdom of Judah, but tribes who maintained a separate capital at Samaria. Some have attempted to dismiss this complicated saga by stating that it is nothing but Supersessionism. However, the ideas behind these various competing theories are far more complicated, especially when Sabbatai Zevi, the "messiah" claimant and his supporters postulated that he represented groups in addition to those identified as being Jews. However, Zevi lost his credibility to all but the Donmeh when he converted to Islam and became an apostate to Judaism in 1666.
During the latter half of the 18th century, variations on this same theory were advocated by some who believed that the British Empire of nations was a manifestation of ancient prophecies recorded in the Book of Genesis predating both the Kingdom of Israel and the Kingdom of Judah.
Others believe that the 'Lost Tribes' simply merged with the local population. For instance, the New Standard Jewish Encyclopedia states "In historic fact, some members of the Ten Tribes remained in Palestine, where apart from the Samaritans some of their descendants long preserved their identity among the Jewish population, others were assimilated, while others were presumably absorbed by the last Judean exiles who in 597-586 [B.C.E.] were deported to Assyria...Unlike the Judeans of the southern Kingdom, who survived a similar fate 135 years later, they soon assimilated