In the aftermath of Moctezuma's great campaign, the armies of the Sun God are swelled by hundreds of tribal recruits. The Zapotec to the south are formidable, yes, but they cannot stand before the blessings of the Gods, the numbers of the tribes, the warriors of Tenochtitlan, and the genius of the Great Leader!
The High Priests of Tenochtitlan urge Moctezuma to secure the Chalco tribes to the East, to strengthen his numerical advantage over the hated Zapotecs. Moctezuma views their advice with suspicion. Perhaps their divinations are simply a test of wit sent from the Gods?
Indeed, it would appear to be so. After consulting Quetzacotl, Moctezuma learns that the Zapotecs have struck a secret alliance with the Chalco tribes. The Chalcos are weak, they would no doubt betray their allies if their was no immediate threat to their homes. It is better to destroy your enemies one by one, so Moctezuma puts off the conquest of Chalco for now.
While the Great Chief waits for his manpower reserves to recover, he recruits a veteran warrior to serve as a secondary commander. A plan is hatched to encircle and destroy the Zapotec armies. This plan would require a great degree of skill and coordination, demanding a competent general. Although the Chief now enjoys numerical superiority, the Zapotecs will not give up their rough landscape easily. A single mistake could mean utter defeat, so planning and leadership are vital.
A few of the Aztlan tribes still resist Moctezuma, preferring their own unenlightened tribal heads. To ensure success in the inevitable Zapotec war, the Chief orders his men to crush and assimilate the troublesome tribes. The tribesmen hear of this, and immediately mobilise against the Chief.
The loyal tribes hold off the traitors, while Moctezuma gathers his forces and moves to crush the blasphemous imbeciles. The Gods will soon feast well.
Moctezuma takes his men on a circuitous route around the main enemy army, crushing the Northern tribes first. A smaller contingent, lead by Commander Tehuetstiquitzin (what?) engages the main army, tying them up for the Great Chief.
The rebellious Huastec tribes are broken. The captives are given to the Sun God, while the remaining free tribes are absorbed into the greater Aztlan whole.
The armies of Huitzilopochtli grow ever mightier.
Relying on the spread of fear from his brutal campaign, Moctezuma sends an envoy to the Western tribes, particularly those based in the Tarasco region. As expected, the local chieftains quickly succumb, and Tenochtitlan grows ever mightier from their tribute.
The peoples of Moctezuma's world all share a similar culture and faith. Despite this similarity, it will take time for the tribes to truly join Tenochtitlan as Aztlan brothers, under the great Sun God. True assimilation will require patience. In the meantime, troublemakers can be sent to the Gods.
Here's one of the issues with native factions. Natives don't get any cavalry (although their rebels do), which on its own is sensible. Unfortunately they suffer the same penalties for this as other countries, so as soon as their army reaches a certain size they suffer this penalty, alongside the basic military disadvantage of lacking cavalry.
The new territories take a toll on Moctezuma's administrative abilities. Relying almost entirely on force of arms to maintain power, continued expansion may well prove to be more than the Great Chief can manage.
Some of the Western tribes have the gall to refuse Moctezuma his tribute. If he didn't have to manage the Zapotec campaign as well, the Chief would crush these treacherous heathens. After the Zapotecs are crushed, they will be fed to the Sun. Their bones will be ground into a fine powder and served to the Chief in a bowl of chocolatl.
The war begins, the tribes assemble. God and carrion bird alike anticipate a great feast.
A two pronged assault is launched. The main body of the Aztlan army, under Moctezuma himself, heads straight for the Zapotecs. Meanwhile, under Tehuetstiquitzin, a contingent of roughly 3000 men march on the Zapotec capital city, high in the hills.
The priesthood is behind the Chief. A wave of prisoners, sacrificial or otherwise, is hotly anticipated in the capital. Moctezuma marches into battle, confident that the Gods are at his back.
But it is not so, and the Gods punish Moctezuma for his hubris. He is beaten, and learns the lesson of humility. The Zapotecs force the Great Chief to flee back to friendly territory, but the Zapotecs follow.
Moctezuma is beaten back further, but the Zapotec victory is not without its cost. The Zapotecs suffer casualties even greater than the Aztlan. Not only that, but the Chief is now fighting on friendly terrain, while the Zapotecs are many miles from home. It may yet be possible to turn their triumph on its head.
While this is going on, Tehuetstiquitzin's contingent eliminates Zapotec reinforcements, giving his Master hope of victory. If Tehuetstiquitzin can reach Moctezuma in time, then their combined forces should prove enough to deliver a crushing blow to the Zapotecs.
Levying hundreds of fresh troops from Tenochtitlan, Moctezuma finds himself once again in command of numerical superiority. Having tasted defeat, Moctezuma found it to be bitter. There is no intention amongst the Chief, nor amongst his men, to repeat the Zapotec disaster. The Chief meets his enemy, whilst Tehuetstiquitzin continues to disrupt enemy reinforcements. The battle could go either way, but in the result of another disaster, Tehuetstiquitzin will be on hand to avert total catastrophe.
But catastrophe is evaded. Despite heavy losses, Moctezuma forces the Zapotec chief to back down. Now it is the enemy that must flee. With extra reinforcements in the form of the contingent, it would seem that the war has swung in Tenochtitlan's favour.
After months of hard fighting, the enemy is finally routed at Tlaxcala. All that remains is to crush pockets of resistance, and to absorb the Zapotecs into glorious Aztlan.
Moctezuma orders his forces to spread out across Zapotec lands, to save him the trouble of crushing each tribe one by one. Overall this should bring the war to a more timely conclusion. It might even be possible to leave only as many men as are needed, and conquer the Chalcos with the rest.
Seeing merit in this plan, Moctezuma gathers what men he can and marches back to Tenochtitlan. After gathering further reinforcements, the Great Chief marches on the Chalcos. After giving up his many prisoners to the Sun God, of course.
The Chalco tribes reluctantly retreat to their hill-forts and villages. The High-Chief musters what men he has against Moctezuma, but, despite his best efforts, he is forced to give ground.
Meanwhile, the Zapotec capital, the only urban settlement in the region really, is captured. Hundreds of prisoners are marched back to Tenochtitlan, and the Gods feast greedily. Blood is a small price to pay, in return for the continued renewal of the Sun.
Moctezuma harries the Chalcos down along the coast, whilst small detachments remain to occupy the various tribal forts and villages.
The Zapotec heartland falls to Aztlan. The Gods are sated with the blood of hundreds, whilst Tenochtitlan benefits from the great plunder, The Chalco lands are much more sparse, but they also yield some riches. It will not be long until both the Chalcos and the Zapotecs bow to glorious Montezuma. Then, the Maya will quake. Perhaps they too will feed great Huitzilopochtli?
The same drama is repeated further North. A brutal conquest, followed by mass enslavement and plunder. Just enough people are left to keep the land from becoming barren, so that Moctezuma's descendants might have an Empire to rule over.
The Chalcos become Aztlan. Those that resist will feed Quetzacotl, Huitzilopochtli, Huehueteot, Tlaloc and mighty Tezcatlipoca. In exchange for their blood, their lands go to Moctezuma and his successors, to rule until the end of the world, which is hardly an immediate concern. The Zapotecs are reduced to but a few scattered forts, and the Maya must already be trembling. Moctezuma's ultimate victory is almost a reality.