The Aztec Empire — what prompted innovation

In 1428, three small cities on the shores of Lake Texcoco went to war against their overlord — and won. That war created the Aztec Empire.

Before 1428, the city of Tenochtitlan Tenochtitlan paid tribute to a nearby power called Azcapotzalco. In 1427, the ruler of Azcapotzalco died and a succession crisis broke out.

Tenochtitlan's ruler, Itzcoatl, saw his chance. He allied with two neighbouring cities — Texcoco and Tlacopan — and together they defeated Azcapotzalco in 1428.

The Triple Alliance: Tenochtitlan, Texcoco and Tlacopan agreed to rule together as the Triple Alliance Triple Alliance. Conquered land and tribute were shared between them, though Tenochtitlan quickly became the dominant partner.

This is the moment IB historians treat as the birth of the Aztec Empire. It matters for our inquiry question — what prompted innovation — because the Alliance itself was an innovation: a new political structure built to survive a crisis and then expand far beyond it.

How a source reveals this: A page from the Codex Mendoza (a pictorial record made for the Spanish colonial government around 1541) lists towns conquered by each Triple Alliance ruler, with tribute goods drawn beside them. Its content directly answers our inquiry question: it shows conquest and tribute-collection were the practical drivers of Aztec expansion from 1428 onward.

Once the Triple Alliance controlled the Valley of Mexico, its rulers faced a new problem: how do you keep an army sharp, capture prisoners for religious sacrifice, and show rival states who is strongest — without risking everything in a full war?

Their answer was the Flower Wars Flower Wars, fought against nearby rival states such as Tlaxcala. These were pre-arranged battles with agreed times and places.

Not just symbolic: Flower Wars were not fake fights. Warriors died in them. But their main goal was different from ordinary conquest warfare — capturing high-status prisoners for sacrifice mattered more than seizing territory.

This is a good example of an imperial reform: a deliberate change to how the state worked, designed to solve the problems of ruling a growing empire. It is exactly the kind of 'innovation' our inquiry question is asking about — not a new tool or building, but a new system.

Reading perspective into a source: A Spanish friar's account written decades after the conquest might describe Flower Wars as savage and irrational. An Aztec pictorial source made before contact would likely frame them as sacred duty. Neither is 'wrong' — they reflect different perspectives perspectives, shaped by who made the source and why.

Moctezuma I Moctezuma I became ruler of Tenochtitlan in 1440, after Itzcoatl's death. His reign (c.1440–1469) is when the Aztec Empire truly took shape.

Moctezuma I pushed Aztec armies far beyond the Valley of Mexico, conquering regions toward the Gulf Coast and the south. Conquered provinces were required to pay tribute — food, cotton, feathers, gold — back to the Triple Alliance.

He also reformed the state itself. He formalised a legal and social code, expanded the class of professional warriors, and strengthened the religious cult of Huitzilopochtli, tying military success directly to religious duty.

Content vs context in a source about Moctezuma I: Imagine a source: an illustrated page from the Codex Mendoza showing Moctezuma I's conquered towns. Its content lists the towns and tribute goods — useful evidence for what he achieved. Its context matters just as much: it was made around 1541, for Spanish administrators, decades after his death — so it may exaggerate imperial order to impress a colonial audience.