<P> During the campaign , Cortés was given support from a number of tributaries and rivals of the Aztecs , including the Totonacs , and the Tlaxcaltecas , Texcocans , and other city - states particularly bordering Lake Texcoco . In their advance , the allies were tricked and ambushed several times by the people they encountered . After eight months of battles and negotiations , which overcame the diplomatic resistance of the Aztec Emperor Moctezuma II to his visit , Cortés arrived in Tenochtitlan on November 8 , 1519 , where he took up residence , welcomed by Moctezuma . When news reached Cortés of the death of several of his men during the Aztec attack on the Totonacs in Veracruz , he took the opportunity to take Moctezuma captive , Moctezuma allowed himself to be captured as a diplomatic gesture . Capturing the cacique or indigenous ruler was standard operating procedure for Spaniards in their expansion in the Caribbean , so capturing Moctezuma had considerable precedent , which might well have included those in Spain during the Christian reconquest of territory held by Muslims . </P>
who was the aztec ruler when the spanish arrived
Moctezuma II