Jamieson, Fausset and Brown on Isaiah 9:5

5. every battle, &c.--rather, "every greave of (the warrior who is) armed with greaves in the din of battle, and the martial garment (or cloak, called by the Latins sagum) rolled in blood, shall be for burning, (and) fuel for fire" [Maurer]. All warlike accoutrements shall be destroyed, as no longer required in the new era of peace (Is 2:4; 11:6, 7; Psa 46:9; Eze 39:9; Mi 5:5, 10; Zec 9:9, 10). Compare Mal 4:1, as to the previous burning up of the wicked.