# They will eat
The word "They" refers to the army of that nation.
# They will beat down with a sword your fortified cities
The sword is a synecdoche for all of the different weapons that people use in war. Alternate translation: "They will use their weapons to conquer your strong cities that you trusted to protect you" (See: [[rc://en/ta/man/jit/figs-synecdoche]])
# your fortified cities
Fortified cities had a wall around them to protect the people inside from their enemies outside.
# in which you put your trust
"that you thought were strong enough to keep you safe"