"He had a wild hate for the relentless foe." Why is Henry so angry at the Confederates? ( Chapter 17 - 18 )

Though still "the youth," Henry has changed from the day before. At the beginning of the fight that day, he is no longer thinking of the metaphoric monsters and war gods that threaten to eat him up. There is no large metaphor that he gives flesh and life –there is only an opposing army, coming at him in his position with an energy he does not feel and cannot understand. This fills him with rage instead of fear. While he thinks of the enemy as beasts having "teeth and claws" and being "flies sucking insolently at his blood," they are still basically men. This is an important change from the day before.