What compelled large numbers of african-americans to head north?

i thinl it is the 1st answer

the lachish letters were written by hoshaiah, a military officer stationed possibly in mareshah,   and sent to yaush, possibly the commanding officer at lachish.

the series of letters were written in carbon ink in ancient hebrew on clay ostraca, shortly before lachish fell to the babylonian army of king nebuchadnezzar in 588/6 bc during the reign of zedekiah, king of judah.