According to Ross Hassig's "Mexico and the Spanish Conquest" the typical Aztec army encompassed about 8000. By his own explanation this could either be all soldiers or a combination of soldiers and porters, depending on how far and where they were marching to. If they were marching somewhere close they didn't need extra supplies. If the march was far, then they would have two choices. Send messengers ahead to allied or tributary towns along the way so that supplies could be readied, or carry extra supplies with them via porters. The rate would be one porter for every four soldiers. This is just one example of course.