Catholic.com
Around 926 b.c., the kingdom of Israel split in two. Up to that point, all twelve tribes of Israel (plus the priestly tribe of Levi) had been united under the monarchies of Saul, David, and Solomon. But when Solomon’s son Rehoboam ascended to the throne, the ten Northern tribes rebelled and seceded from the union. This left only two tribes—Judah and Benjamin (plus much of Levi)—under the control of the king in Jerusalem. From that time on, the tribes were divided into two nations, which came to be called the House of Israel (the Northern ten tribes) and the House of Judah (the Southern two tribes).
This situation continued until around 723 B.C., when the Assyrians conquered the Northern kingdom. To keep conquered nations in subjection, it was Assyrian policy to break them up by deporting their native populations to other areas and resettling the land with newcomers. When the House of Israel was conquered, most people belonging to the ten Northern tribes were deported and settled elsewhere in the Assyrian kingdom, including places near Nineveh, Haran, and on what is now the Iran-Iraq border. They were replaced by settlers from locations in or near Babylon and Syria.
These settlers intermarried, together with the remaining Israelites, and became the Samaritans mentioned in the New Testament (a few hundred of whom still survive today). The Israelites who had been deported also intermarried with the peoples of the places where they had been resettled. They eventually lost their distinct identity, disappeared, and their culture was lost to history. Some refer to them as "the lost tribes of Israel."
A movement called "British Israelism" claims to have found the ten "lost tribes," however, and in some very unlikely places.
For many years, one of the leaders in the British Israelism movement was Herbert W. Armstrong, founder of the self-proclaimed "Worldwide Church of God." Especially for Americans, Armstrong was