Of all the battles of Aegon's Conquest, none was so great or so terrible as the one the singers named the Field of Fire. When word spread that the dragon had come, King Mern IX Gardener of the Reach and King Loren I Lannister of the Rock, ancient rivals both, set aside their enmity and joined their strength against the invader. Between them they mustered the largest army ever seen in Westeros, some fifty-five thousand men by the counts that have come down to us, with near six hundred knights and lords riding beneath their banners of green and gold and crimson. Against this host Aegon Targaryen could set fewer than a tenth as many swords, and so he did not trust to swords at all.
The two armies met upon the plains south of the Blackwater Rush, amid fields of golden wheat ripe for the harvest. There Aegon brought all three of his dragons into battle together, the only time in his life he ever did so: Balerion the Black Dread beneath the Conqueror himself, Vhagar beneath Queen Visenya, and Meraxes beneath Queen Rhaenys. The dry fields caught at once, and the great host was wrapped in flame. Men and horses alike burned or broke and fled, trampling their own in the press. Near four thousand died in the fire, and near a thousand more of Aegon's own men perished besides, some slain by the foe and some by the dragonflame that spared neither friend nor enemy. King Mern IX Gardener died there upon the field, and with him fell his sons and grandsons and brothers, so that the green hand of House Gardener, which had ruled the Reach since the age of Garth Greenhand, was snuffed out entire.
King Loren of the Rock escaped the burning and fled, but on the morrow he thought better of dying for a crown and returned to bend his knee. Aegon raised him up, forgave him, and confirmed him as Lord of Casterly Rock and Warden of the West, the first of the great kings to yield and keep his seat. Highgarden and the lordship of the Reach Aegon granted to Harlen Tyrell, the Gardeners' own steward, who had opened the castle gates without a fight. Ever after, the scorched plain was known as the Field of Fire, and its lesson was not lost upon the lords of Westeros: no army, however vast, could stand against a dragon in the open.