By about 1400, three city-states had grown into small empires. In 1428, these two empires fought the Tepanec War for control of the area. The Texcoco empire made an alliance with some other powerful city-states, including Tenochtitlan, and won the war. These allies were supposed to share power equally as they started to gain control of more land. However, by 1430, Tenochtitlan became the most powerful member of the alliance. It became the capital city of the Aztec Empire, and its ruler became the 'high king' of the Empire.