en_tn_condensed/jer/51/27.md

Lift up a signal flag ... Blow the ram's horn ... Call ... to attack

Lifting a signal flag and blowing a ram's horn are both ways of calling people to attack. (See: rc://en/ta/man/jit/figs-parallelism)

signal flag

"battle flag." This is large flag for the soldiers to follow in battle.

attack her

The city of Babylon is a metonym for the people of Babylon, and it is spoken of as if it were a woman. Alternate translation: "attack the people of Babylon" (See: rc://en/ta/man/jit/figs-metonymy and rc://en/ta/man/jit/figs-metaphor)

Ararat ... Minni ... Ashkenaz

These are names of nations or people groups. (See: rc://en/ta/man/jit/translate-names)

bring up horses like swarming locusts

Yahweh compares a great number of horses to a swarm of locusts. Alternate translation: "bring many horses with soldiers quickly" (See: rc://en/ta/man/jit/figs-simile)