Albert Barnes Commentary Lamentations 1:3

"Judah is gone into captivity because of affliction, and because of great servitude; She dwelleth among the nations, she findeth no rest: All her persecutors overtook her within the straits." — Lamentations 1:3 (ASV)

Because of ... – that is, the people, not of Jerusalem only, but of the whole land, is gone into exile to escape from the affliction and laborious servitude, to which they are subject in their own land.

Persecutors ... between the straits – Rather, pursuers ... in the midst of her straits. The Jews flee like deer to escape from the invading Chaldeans, but are driven by them into places from where there is no escape.