The traditional way of fighting battles, and the way in which King Lot and the Gaelic Confederation were going to fight, is that the kerns (the serfs or foot soldiers) fight on the outer circle, while the nobles fight in the inner circle. The nobles do not really fight one another, but observe a form of ritual while the kerns shed blood and make the numbers to win or lose. But King Arthur has decided not to fight in the traditional manner; he has come to learn the value of each kern's life and orders his knights to truly fight.
Here, Arthur introduces the practice of total warfare. He demolishes the ritualistic aspects to warfare, instead wanting not to hide the brutal and inhuman act of killing behind something idealized. In writing these scenes, White is also arguing against the practice of propaganda during WWII: propaganda attempted to depict the war as something romantic and courageous, when it was in fact brutal, inhuman and violent.
Arthur begins the battle by not observing the traditional hour for warfare. Instead, he attacks by night. Arthur is wildly outnumbered; torches flare and the cries of battle linger over the ground. His start is rewarded with success.
The notion that there might be a "traditional hour" for warfare is peculiar; both this and Arthur's subversion of the convention draws attention to the ironically inhumane nature of warfare previously—in which the violence was concealed by a veil of chivalry and romanticism.
At around noon, King Lot recognizes he is being dealt a different kind of warfare. Lot's nerve begins to waver; he is wounded in the shoulder. When the sun sets, Arthur calls off the attack although they are close to victory. The exhausted armies sleep. At daybreak, Arthur attacks again. At noon, the allied kings break in a spectacle of shattered lances and debris.
Arthur's attack on King Lot is perhaps disrespectful as he catches him off guard. But Arthur wishes simply for the battle to be done with so he can begin his rule to end all battles.