When were the tribes of Judah and Benjamin taken to Babylon?
The southern two tribes of Judah and Benjamin, which we call Judah, were taken captive all the way to Babylon about 150 years after the ten tribes went into captivity into Syria around 775 B.C.; only a few thousand returned after the 70 years.
The context explains that the ten tribes of the southern kingdom went into captivity into Syria about 775 B.C. and never really came back as tribes, which is why some people call them the lost tribes. About 150 years later, the southern two tribes of Judah and Benjamin, collectively called Judah, were taken captive all the way to Babylon. Only a few thousand returned after the 70 years. The rest were assimilated into the whole Middle East. This pattern is compared to immigrants in America who gradually lose their mother tongue over two or three generations.