 The most significant event of his reign—and of Quiriguá's history—occurred in AD 738 (9.15.6.14.6 on the Mayan calendar), when his forces defeated the city of Copán.The ruler of Copán, Uaxaclajuun Ubʼaah Kʼawiil (formerly known as "18 Rabbit") was captured and later beheaded.Before Kʼakʼ Tiliw Chan Yopaat's bold move, Quiriguá had been a vassal of Copán.