Who is War/Mars from On a Pale Horse and what is their importance?

The personification War, also known as Mars, is an Incarnation, like Death. War is an immortal office held by a human soul. Mars sees death in war as giving glory to the dying soldiers, an everlasting benefit that can't be won in any other way. He also sees war as a necessary part of life and creating social change. War helps Zane realize that to fight Satan, he must use his weapon, his magic scythe.