The man who bends the bow, and the heavy-armed soldier who vaunts himself in his coat of mail (Jeremiah 46:4 note), represent the Babylonians who defend the city.
Related Commentaries of Jeremiah 51:3
Jeremiah 51:3
3 Against him that bendeth let the archer bend his bow, and against him that lifteth himself up in his brigandine: and spare ye not her young men; destroy ye utterly all her host.