The fleet that ultimately left Cuba comprised 11 ships. Cortés had 530 Europeans, including 30 crossbowmen, and 12 with muzzle-loaded hand-guns - weapons that proved deadly and unnerving to the Aztecs. He also had 14 small pieces of artillery and some portable breech-loading cannon on the ships.

Along with nearly a hundred sailors, there was also a doctor, several carpenters and at least eight women, one of whom would later proudly call herself a "conquistadora." There were many non-Europeans, including several hundred Cuban Indians and some Africans, both freemen and slaves. Cortés also took a Mayan-speaking Indian fisherman who had been captured in the Yucatan on an earlier expedition.

Cortés' secret weapon was 16 horses, which the native Americans had never before seen. There were also many dogs, wolfhounds and mastiffs. In Europe, the use of dogs in war was common and they were deployed with horrible effect in the New World where, once again, the Indians had never seen such creatures.