1521
Fall (Siege) of Tenochtitlan
The setting
Tenochtitlan, Lake Texcoco, Valley of Mexico
Island city on a lake, connected by causeways; urban canals
Reveal the outcome
Recorded sideAztec Triple Alliance
Recorded resultdestruction of the city and capture of the emperor
After a roughly three-month siege, the Spanish-led coalition cut off the city, controlled the lake with brigantines, starved and stormed it, and captured Cuauhtemoc
How the atlas explains it
Cortes used brigantines to dominate Lake Texcoco, severing the causeways and the city's food and fresh-water supply, then ground inward in combined-arms urban assaults backed by overwhelming native-ally manpower. Decisively, a smallpox epidemic (introduced via the Spanish, 1520) had already devastated the defenders and killed earlier leadership before and during the siege (disease impact widely cited, exact mortality disputed).
What followed
Ended the Aztec empire and established Spanish rule in central Mexico (later Mexico City).