At his right hand was the divination for Jerusalem, to appoint captains, to open the mouth in the slaughter, to lift up the voice with shouting, to appoint battering rams against the gates, to cast a mount, and to build a fort.
At his right hand - rather, 'In his right hand was (is) the divination for Jerusalem' - i:e., he holds up in his right hand the arrow marked with "Jerusalem," to encourage his army to march for it.
To appoint captains - the margin, 'battering-rams,' adopted by Fairbairn, is less appropriate; because "battering-rams "follow presently after (Grotius).
To open the mouth in the slaughter - i:e., commanding slaughter. Not as Gesenius, 'to open the mouth with the war-shout.'