Possible meanings are 1) this is a metonym for death in battle. Alternate translation: "in battle" or 2) they will be killed by literal swords. (See: [[rc://en/ta/man/translate/figs-metonymy]])
These three phrases have the same meaning and emphasize that Nebuchadnezzar will deal severely with them. Alternate translation: "He will not show them any mercy or compassion at all" (See: [[rc://en/ta/man/translate/figs-doublet]])