Théoden King of the Mark had reached the road from the Gate to the River, and he turned towards the City that was now less than a mile distant. He slackened his speed a little, seeking new foes, and his knights came about him, and Dernhelm was with them. Ahead nearer the walls Elfhelm's men were among the siege-engines, hewing, slaying, driving their foes into the fire-pits. Well nigh all the northern half of the Pelennor was overrun, and there camps were blazing, orcs were flying towards the River like herds before the hunters; and the Rohirrim went hither and thither at their will. But they had not yet overthrown the siege, nor won the Gate. Many foes stood before it, and on the further half of the plain were other hosts still unfought. Southward beyond the road lay the main force of the Haradrim, and there their horsemen were gathered about the standard of their chieftain. And he looked out, and in the growing light he saw the banner of the king, and that it was far ahead of the battle with few men about it. Then he was filled with a red wrath and shouted aloud, and displaying his standard, black serpent upon scarlet, he came against the white horse and the green with great press of men; and the drawing of the scimitars of the Southrons was like a glitter of stars.
Then Théoden was aware of him, and would not wait for his onset, but crying to Snowmane he charged headlong to greet him. Great was the clash of their meeting. But the white fury of the Northmen burned the hotter, and more skilled was their knighthood with long spears and bitter. Fewer were they but they clove through the Southrons like a fire-bolt in a forest. Right through the press drove Théoden Thengel's son, and his spear was shivered as he threw down their chieftain. Out swept his sword, and he spurred to the standard, hewed staff and bearer; and the black serpent foundered. Then all that was left unslain of their cavalry turned and fled far away.
~The Battle of the Pelennor Fields, RotK