The Golden Tooth is the mountain fastness of House Lefford that guards the eastern road out of the westerlands, and the pass beneath it is the gate through which any host must march to carry war between Casterly Rock and the riverlands. When Lord Tywin Lannister loosed his sons and his strength upon the Trident in 298 AC, it was through this pass that Ser Jaime Lannister led the first Lannister host toward Riverrun.
The river lords, under Lords Vance and Piper, gathered to hold the narrow ground and deny the pass, hoping that the difficulty of the terrain would blunt the Lannister numbers. It availed them little. Jaime fell upon them and shattered their lines in short order, scattering the defenders and leaving the road east open behind him. The victory was swift and near total, and it set the pattern for the opening of the war in the west: the river lords broken piecemeal before the Tullys could bring their full strength to bear. From the Golden Tooth Jaime marched unopposed into the riverlands and turned his host toward Riverrun and the ailing Lord Hoster Tully.