For all their numbers the free folk were a people, not an army, ill-armored and without cavalry or discipline, and it was upon this weakness that their doom turned. As Mance Rayder's host lay encamped in the haunted forest before the gates of Castle Black, spent by days of fruitless assault, a mounted host descended upon them from the south. Stannis Baratheon, having taken warning of the Watch's peril and answered its plea when the great lords of the realm would not, had shipped his remaining strength north to Eastwatch-by-the-Sea and marched hard upon the Wall.
The stroke was swift and merciless. Stannis flung his knights against the wildlings in a double envelopment, mailed horsemen sweeping in from either flank against a foe that had no answer to a cavalry charge. The free folk, weary and unhorsed and taken wholly by surprise, broke and were ridden down in their thousands among the trees. Their line dissolved, and the great host that had taken years to gather was scattered in a single afternoon. Mance Rayder himself was taken alive, and with him the last hope of the free folk to pass beneath the Wall by force of arms.
The victory made Stannis Baratheon master of the Wall and the first king in memory to bring an army to the defense of the realms of men. He claimed the loyalty of a broken people, spared many of the free folk who would give him their allegiance, and took Castle Black for his seat in the north while he weighed his war against the Boltons and the Iron Throne. The maesters mark the battle beneath the Wall as the ruin of Mance Rayder's cause and the beginning of a stranger chapter still, in which a claimant to the Iron Throne made common cause with wildlings against the winter.