text: Ambassadors Once the Aztecs had decided to conquer a particular city (Altepetl), they sent an ambassador from Tenochtitlan to offer the city protection. They would showcase the advantages cities would gain by trading with the empire. The Aztecs, in return, asked for gold or precious stones for the Emperor. They were given 20 days to decide their request. If they refused, more ambassadors were sent to the cities. However, these ambassadors were used as up front threats. Instead of trade, these men would point out the destruction the empire could and would cause if the city were to decline their offer. They were given another 20 days. If they refused the Aztec army was sent immediately. There were no more warnings. The cities were destroyed and their people were taken as prisoners.
  Messengers
  The Aztecs used a system in which men stationed approximately  apart along main roads relayed messages from the empire to armies in the field or to distant cities and vice versa. For example, the runners might be sent by the king to inform allies to mobilize if a province began to rebel. Messengers also alerted certain tributary cities of the incoming army and their food needs, carried messages between two opposing armies, and delivered news back to Tenochtitlan about the outcome of the war. While messengers were also used in other regions of Mesoamerica, it was the Aztecs who apparently developed this system to a point of having impressive communicative scope.