"Yax-Pasah, the last king of Yax-K'uk'-Mo's dynasty, added his own statement to Waxaklahun-Ubah-K'awil's program of stelae [in the form of three snake altars pictured above]. His motivation may have been to recoup the honor of his ancestor, who had met an ignominious end at the hands of K'ak'-Tiliw of Quirigua.
Waxaklahun-Uban-K'awil's last year was spent on rebuilding the ballcourt, which he dedicated on 184.108.40.206.13 (January 10, 738). One hundred and seven days later, K'ak'-Tiliw, who had come to office under Waxaklahun-Ubah-K'awil's authority, turned on his overlord and captured the unfortunate Waxaklahun-Ubah-K'awil. His motivation may have been personal ambition, but he was also involved in the power politics of the great alliances. A lord from Kalak'mul, Tikal's great enemy, celebrated a period ending at Quirigua a year before this war. The Quirigua rebellion signaled Kalak'mul's intervention into the politics of the southeastern zone and perhaps a bid for control of the Motagua drainage and the trade in jade and obsidian.
In any case, we think that Waxaklahun-Ubah-K'awil moved against his vassal to prevent him from or to punish him for changing sides. But the Quirigua king prevailed. Perhaps a factor in his victory was that he was a young king in his prime facing a man who had been ruling for close to forty-three years. Waxaklahun-Ubah-K'awil was well past his prime as a warrior at the time of the battle.
K'ak'-Tiliw not only captured his overlord, but according to the inscriptions, he also chopped up and burned the statues of Copan's patron gods. Destroying your enemies' gods robbed them of their supernatural protection. Six days after destroying the gods, he decapitated Waxaklahun-Ubah-K'awil, on 220.127.116.11.6 (May 3, 738)."
Linda Schele & Peter Mathews, The Code of Kings: The Language of Seven Sacred Maya Temples and Tombs, p. 170-71