Zapotec civilization originated in the Central Valleys of Oaxaca in the late 6th century BC.
The three valleys were divided among three different-sized societies, separated by 80 square kilometres (31 sq mi) “no-man’s-land” in the middle.
The city of Oaxaca much later developed in that area.
Archaeological evidence, such as burned temples and sacrificed war captives, suggests that the three societies competed against each other.
At the end of the Rosario phase (700–500 BC), the valley's largest settlement San José Mogote, and a nearby settlement in the Etla valley, lost most of their population.

During the same period, a new large settlement developed in the “no-man’s-land” on top of a mountain overlooking the three valleys; it was later called Monte Albán.
Early Monte Albán pottery is similar to pottery from San José Mogote, which suggests that the newer city was populated by people who had left San José Mogote.
Although there is no direct evidence in the early phases of Monte Albán's history, walls and fortifications around the site during the archaeological phase Monte Alban 2 (ca.
100 BC–200 AD) suggest that the city was constructed in response to a military threat.
American archaeologists Joyce Marcus and Kent V. Flannery liken this process to what happened in ancient Greece - synoikism: a centralization of smaller dispersed populations congregated in a central city to meet an external threat.

The Zapotec state formed at Monte Albán began to expand during the late Monte Alban 1 phase (400–100 BC) and throughout the Monte Alban 2 phase (100 BC – AD 200).
During Monte Alban 1c (roughly 200 BC) to Monte Alban 2 (200 BC – AD 100), Zapotec rulers seized control of the provinces outside the valley of Oaxaca because none of the surrounding provinces could compete with them politically and militarily.
By 200 AD, the Zapotec had extended their influence, from Quiotepec in the North to Ocelotepec and Chiltepec in the South.
Monte Albán had become the largest city in what are today the southern Mexican highlands, and retained this status until approximately 700 AD.

The expansion of the Zapotec empire peaked during the Monte Alban 2 phase.
The Zapotec conquered or colonized settlements far beyond The Valley of Oaxaca.
Most notably, their influence is visible in the sudden change in style of ceramics made in regions outside the valley.
These regions' unique styles were suddenly replaced with Zapotec-style pottery, indicating their integration into the Zapotec empire.

Archaeologist Alfonso Caso, one of the first to conduct excavations in Monte Albán in the 1930s, argued that a building on the main plaza of Monte Albán is further evidence for the dramatic expansion of the Zapotec state.
What today is called Building J is shaped like an arrowhead, unlike other monumental buildings.
It displays more than 40 carved stones with hieroglyphic writing.
Archaeologists interpreted the glyphs to represent the provinces controlled by the Zapotec.
Each glyph group also depicts a head with an elaborate head dress carved into the slabs.
These are assumed to represent the rulers of the provinces.
Heads turned upside down are believed to represent the rulers killed and whose provinces were taken by force, while the upright ones may represent those who did not resist colonization and had their lives spared.
For this reason, Building J is also referred to by archeologists as “The Conquest Slab”.

Marcus and Flannery write about the subsequent dramatic expansion of the Monte Albán state, noting when there is 
"a great disparity in populations between the core of a state and its periphery, it may only be necessary for the former to send colonists to the latter.
Small polities, seeing that resistance would be futile, may accept a face-saving offer.
Larger polities unwilling to lose their autonomy may have to be subdued militarily.
During the expansion of Monte Alban 2 state, we think we see both colonization and conquest".
Zapotec civilization originated in the Central Valleys of Oaxaca in the late 6th century BC. The three valleys were divided among three different-sized societies, separated by 80 square kilometres (31 sq mi) “no-man’s-land” in the middle. The city of Oaxaca much later developed in that area. Archaeological evidence, such as burned temples and sacrificed war captives, suggests that the three societies competed against each other. At the end of the Rosario phase (700–500 BC), the valley's largest settlement San José Mogote, and a nearby settlement in the Etla valley, lost most of their population. 
During the same period, a new large settlement developed in the “no-man’s-land” on top of a mountain overlooking the three valleys; it was later called Monte Albán. Early Monte Albán pottery is similar to pottery from San José Mogote, which suggests that the newer city was populated by people who had left San José Mogote. Although there is no direct evidence in the early phases of Monte Albán's history, walls and fortifications around the site during the archaeological phase Monte Alban 2 (ca. 100 BC–200 AD) suggest that the city was constructed in response to a military threat. American archaeologists Joyce Marcus and Kent V. Flannery liken this process to what happened in ancient Greece - synoikism: a centralization of smaller dispersed populations congregated in a central city to meet an external threat.
The Zapotec state formed at Monte Albán began to expand during the late Monte Alban 1 phase (400–100 BC) and throughout the Monte Alban 2 phase (100 BC – AD 200). During Monte Alban 1c (roughly 200 BC) to Monte Alban 2 (200 BC – AD 100), Zapotec rulers seized control of the provinces outside the valley of Oaxaca because none of the surrounding provinces could compete with them politically and militarily. By 200 AD, the Zapotec had extended their influence, from Quiotepec in the North to Ocelotepec and Chiltepec in the South. Monte Albán had become the largest city in what are today the southern Mexican highlands, and retained this status until approximately 700 AD.
The expansion of the Zapotec empire peaked during the Monte Alban 2 phase. The Zapotec conquered or colonized settlements far beyond The Valley of Oaxaca. Most notably, their influence is visible in the sudden change in style of ceramics made in regions outside the valley. These regions' unique styles were suddenly replaced with Zapotec-style pottery, indicating their integration into the Zapotec empire.
Archaeologist Alfonso Caso, one of the first to conduct excavations in Monte Albán in the 1930s, argued that a building on the main plaza of Monte Albán is further evidence for the dramatic expansion of the Zapotec state. What today is called Building J is shaped like an arrowhead, unlike other monumental buildings. It displays more than 40 carved stones with hieroglyphic writing. Archaeologists interpreted the glyphs to represent the provinces controlled by the Zapotec. Each glyph group also depicts a head with an elaborate head dress carved into the slabs. These are assumed to represent the rulers of the provinces. Heads turned upside down are believed to represent the rulers killed and whose provinces were taken by force, while the upright ones may represent those who did not resist colonization and had their lives spared. For this reason, Building J is also referred to by archeologists as “The Conquest Slab”.
Marcus and Flannery write about the subsequent dramatic expansion of the Monte Albán state, noting when there is 
"a great disparity in populations between the core of a state and its periphery, it may only be necessary for the former to send colonists to the latter. Small polities, seeing that resistance would be futile, may accept a face-saving offer. Larger polities unwilling to lose their autonomy may have to be subdued militarily. During the expansion of Monte Alban 2 state, we think we see both colonization and conquest".
Zapotec civilization