Moctezuma I (1440–69) established a Triple Alliance with the neighbouring city-states of Texcoco and Tlacopan, which would become the Aztec instrument of empire. He extended Aztec dominion to the Gulf coast, subduing the Huastecs. More mettlesome opponents were found closer to home: the Chalco city-state at the southern end of Lake Texcoco was only annexed after 20 years of warfare, and the Tlaxcalans resisted all Aztec attempts at conquest, remaining an independent island in Aztec territory. Captives taken in these campaigns were sacrificed in mass ritual executions, presided over by the king in person and his high priest. Between genuine military expeditions, the Aztec engaged neighbouring tribes in ritual battles, ‘flower wars’, which served as combat training, and a means to showcase Aztec martial prowess. Moctezuma’s successor, Axayacatl, (1469–81) – the name means ‘water-boatman’, an aquatic insect – conquered Tuxpan, Tlatelolco and the Toluca Valley, but was defeated by the Tarascans.