From its beginning, the Aztec Empire was a work in progress. Power struggles among rivals and wars to acquire new territory were ongoing occurrences. About a century before the Spanish conquest, three major groups vied for supremacy—the Mexicas, Tenochas, and Acolhuas. Their territories adjoined each other, with the Mexicas situated between the other two. To balance the power and reduce the frequency of wars, these three groups formed the Triple Alliance in the early fifteenth century. However, the Mexicas dominated the alliance, eventually becoming undisputed lords of the Valley of Mexico and many other territories beyond the confines of the valley.

The Capital City at Tenochtitlán

The most visible symbol of Aztec supremacy was Tenochtitlán, the capital city built on an island in Lake Texcoco. In the early years after its founding, Tenochtitlán was much like...