Aztec Wars of Expansion (c. 1428–1502)

PRINCIPAL COMBATANTS: Aztecs vs. rival tribes; during a
brief civil war, the rival Aztec cities of Tenochtitlán and
Tlatelolco fought.

PRINCIPAL THEATER(S): Mexico

DECLARATION: None

MAJOR ISSUES AND OBJECTIVES: Imperial expansion

OUTCOME: The Aztecs conquered and subjugated most
rival tribes, primarily to the south of their capital at
Tenochtitlán (modern Mexico City).

APPROXIMATE MAXIMUM NUMBER OF MEN UNDER ARMS: At
the Battle of Zamacuyahuac the Aztecs fielded 24,000 men.

CASUALTIES: At the Battle of Zamacuyahuac the Aztecs
lost 20,000 men.

TREATIES: No documents have been identified.

The Aztecs first appeared as a nomadic warrior tribe who
settled on two islands in Mexico’s Lake Texcoco, Tenochtitlán
and Tlatelolco, about 1325. These island locations
were natural fortresses from which the Aztecs waged a
series of expansionist wars against lesser tribes.
During the reign of the “Black Serpent,” Emperor Itzcoatl
(1428–40), the Aztecs fought the Tepanaca tribe,
who lived on the western shore of Lake Texcoco. This
tribe, correctly fearing Aztec aggression, attempted to
blockade Tenochtitlán and Tlatelolco, effectively holding
the Aztecs under siege and cutting off all supplies, including
water. Itzcoatl led an expedition against the Tepanaca
in 1428. It developed into a prolonged war, but by 1430
the Aztecs had gained the initiative and laid siege to the
rival tribe in its own capital. With the Tepanaca crushed,
Itzcoatl took the war to its ally, the people of the city of
Xochimilco, which fell in 1433, bringing the first phase of
Aztec aggression to an end.
Under Montezuma I (also called Moctezuma I, or
Ilhuicamina, “One Who Frowns Like a Lord”), the Aztecs
undertook an even more aggressive campaign of expansion.
From 1440 to 1468, the span of this emperor’s reign,
the Aztec Empire was pushed far to the south of Tenochtitlán.
Montezuma I established the Aztecs as a powerful
trading people, and the empire flourished.
Montezuma I was succeeded by Axayactl, who pressed
the Aztec program of expansion eastward all the way to
the Gulf of Mexico. At the same time he further enlarged
the Aztec sphere of influence to the southwest, stopping
only at the Pacific coast.
In 1473 a civil war (sometimes called the War of Defilement)
broke out between Tenochtitlán and Tlatelolco.
Tlatelolco struck alliances with other Aztec cities opposed
to the power of Tenochtitlan. However, Tlatelolco unwisely
provoked war prematurely, before any of its allies could be
brought to bear on the conflict, and Tenochtitlán acted
swiftly to crush its rival.
The next recorded Aztec war came five years later, in
1478. Tenochtitlán at this point had become the central
city of a three-city league, which included Tlacopán and
Texcoco. The league launched a war against the Tarascans,
a traditional mutual enemy. Under Axayactl’s inept command,
however, the army of the league was deployed in a
piecemeal and divided fashion. This violation of a timeless
tactical principle—never divide your forces in the face of
the enemy—brought on disaster at the Battle of Zamacuyahuac.
On the first day of the battle, the Aztec forces
were defeated in detail. Axayactl regrouped on the second
day and led a make-or-break charge against the Tarascans.
The result was an even worse defeat. Of 24,000 league
forces deployed, all but 4,000 fell in battle.
By 1481 the Aztecs had fully recovered from the disaster
at Zamacuyahuac, and in the six-year reign of Emperor
Tizoc, from 1481 to 1486, they pushed the frontier of their
empire to the southeast. On balance, the Aztecs gained significant
territory, although the war of expansion was by no
means an unqualified success. The era of true imperial triumph
came under the reign of Ahuitzotol, from 1486 to
1502, when Aztec forces made an extensive sweep, primarily
far to the south. These southern acquisitions spanned
both coasts.

See also SPANISH CONQUEST OF MEXICO.

Further reading: Frances Berdan, The Aztecs of Central
Mexico: An Imperial Society (Fort Worth, Tex.: Harcourt
Brace College, 1990); John Bierhorst, tr., History and
Mythology of the Aztecs: The Codex Chimalpopoca (Tempe:
University of Arizona Press, 1998); Ross Hassig, War and
Society in Ancient Mesoamerica (Berkeley: University of
California Press, 1992); Richard F. Townsend, The Aztecs
(London and New York: Thames and Hudson, 2000).