In a few weeks this was done. King Ban of Brittany and his brother, King Bors, crossed into Britain with five thousand good knights, sworn to aid Arthur in this great conflict.
With King Ban came his son, young Lancelot, who was later to make more fame and more dole than any knight of Arthur's court.
On a day in early spring, the hosts of Arthur and his two allies were encamped in Sherwood Forest, and the fore-riders or scouts, which Merlin had sent out, came hastening in to say that the host of the eleven kings was but a few miles to the north of Trent water. By secret ways, throughout that night, Merlin led the army of Arthur until they came near where the enemy lay. Then did he order an ambush to be made by some part of their men, with King Ban and King Bors, by hiding in a hollow filled with trees.
In the morning, when either host saw the other, the northern host was well comforted, for they thought King Arthur's force was but small.
With the pealing of trumpets and the shouts of the knights, King Arthur ordered his men to advance, and in their midst was the great silken banner with the fierce red dragon ramping in its folds. This had been blessed by the Archbishop of London at a solemn service held before the host left London.
All day the battle raged. Knight hurled and hurtled against knight, bowmen shot their short Welsh arrows, and men-at-arms thrust and maimed and slashed with the great billhooks and spears.
King Arthur, with his bodyguard of four—Sir Kay, Sir Baudwin, Sir Ulfius, and Sir Bedevere—did feats of arms that it was marvel to see. Often the eleven kings did essay to give deadly strokes upon the king, but the press of fighting kept some of them from him, and others withdrew sore wounded from the attack upon him and his faithful four.
Once the five held strong medley against six of the rebel kings, and these were King Lot, King Nentres, King Brandegoris, King Idres, King Uriens, and King Agwisance; and so fiercely did they attack them that three drew off sore wounded, whilst King Lot, King Uriens and King Nentres were unhorsed, and all but slain by the men-at-arms.
At length it appeared to Arthur that his host was yielding before the weight of numbers of the enemy, and then he bethought him of a strategy. He took counsel of his nobles, and they approved; he sent a trusty messenger to the Kings Ban and Bors, who still lay in ambush; and then, commanding his trumpets to sound, he ordered a retreat.
As had been agreed on, the knights on Arthur's side made their retreat in a confusion that seemed full of fear; and the enemy, joyfully shouting their cries of triumph, pursued them headlong.