In 1165, Benjamin ben Jonah departed from Tudela on a journey in search of Jewish communities. In 1171 he returned to Spain and wrote his memoirs, the famous Journeys of Benjamin of Tudela. Regarding the Ten Tribes, he wrote: "... and it is said that there are people there who are the tribe of Reuben and Gad and half the tribe of Manassehâ€¦ and they went and built great, fortified cities, and they fight against all the kingdoms, and none can enter them. For 18 days one walks in the uninhabited deserts, until one comes to Khievar, a very great city with some 50,000 Jews, including scholars and warriors, who fight against the sons of Shinar and the northern lands, and the nearby land of Aliman, which is the beginning of India."
Maimonides in one of his letters, wrote: "With regard to your question about the tribes, you should know that this is a true issue and we wait for their arrival, for they are hidden beyond the mountains of darkness, and the river Gozan and the river Sambatyon."
In Israel the subject arose in the 1980s when Rabbi Eliahu Avichail of Jerusalem founded the Amishav movement and discovered the lost tribes of Bnei Menashe in Mizoram and Manipur, in northeastern India. Another organization active in this effort is Shavei Israel, headed by Michael Freund.
Dr. Avigdor Shachan, a lecturer in military history, published his book Across the Sambatyon in 2005, in which he recounts the migration routes of the exiled Ten Tribes from the Land of Israel to Assyria, and from there across Asia Minor, Iran, Afghanistan, India, China and Japan. His conclusions were that in these areas there continue to live millions of people who maintain remnants of customs that connect them to ancient Israel, despite the passing of 2,700 years.
The last writer on this subject is Hillel Halkin, who in his On the Banks of the Sambatyon: A Journey in the Footsteps of the Descendants of Menashe" presented the question of the origin of Bnei Menashe. Halkin, somewhat skeptically, accompanied Avichail to Manipur and Mizoram, was impressed that there indeed exists an unsolved mystery, returned twice to research it further and slowly concluded that this lost tribe has a connection to the people of Israel.
It is important to mention that the Ten Tribes never disappeared from the awareness of their Judean brethren. Most scholars of Israelite history are of the opinion that the residents of the Samarian kingdom intermingled rather swiftly among the peoples to which they arrived, were swallowed up among them and intermarried until they completely lost their identity.