Albert Barnes Commentary Jeremiah 52:25

"and out of the city he took an officer that was set over the men of war; and seven men of them that saw the king`s face, that were found in the city; and the scribe of the captain of the host, who mustered the people of the land; and threescore men of the people of the land, that were found in the midst of the city." — Jeremiah 52:25 (ASV)

An eunuch ... men of war - Or, who had charge of men of war. The King James Version makes him commander-in-chief; he was second in command, that is, a lieutenant, possibly one among many others of equal rank.