fort - rather, “watch-tower” (Jer 52:4) wherein the besiegers could watch the movements of the besieged [Gesenius]. A wall of circumvallation [Septuagint and Rosenmuller]. A kind of battering-ram [Maurer]. The first view is best.
a mount - wherewith the Chaldeans could be defended from missiles.
battering-rams - literally, “through-borers.” In Eze 21:22 the same Hebrew is translated “captains.”