Tepanec War

The Tepanec War broke out following a 1426 succession crisis in Azcapotzalco, the capital of the dominant Tepanec state in the Valley of Mexico, after the death of its longtime ruler Tezozomoc. The usurper Maxtla seized the Tepanec throne, turned against the Mexica ruler of Tenochtitlan, Chimalpopoca, and later placed Tenochtitlan under blockade, driving the city, along with the neighboring cities of Texcoco and Tlacopan, into open rebellion against Tepanec overlordship. The allied forces of Tenochtitlan, Texcoco and Tlacopan defeated Azcapotzalco in 1427 and 1428, breaking Tepanec dominance in the valley. In 1430 the three victorious cities formalized their wartime cooperation into the Triple Alliance, an arrangement to jointly conduct future conquests and divide the resulting tribute, which grew over the following century into the dominant power of central Mexico commonly known as the Aztec Empire.