The reductions did not begin with coercion. They began with an offer. By the early 17th century, the Spanish encomienda system had reduced indigenous peoples across South America to forced laborers, and the Guaraní bore that burden directly. In 1609, acting under orders from Philip III, the Spanish governor of Asunción struck a deal with the Jesuit Provincial of Paraguay: the order would establish settlements along the Paraná River, populated by indigenous people and kept separate from Spanish towns. For the Guaraní, the missions offered something the colonial world otherwise denied -- protection from enslavement and from the forced labor of the encomienda. That protection was real enough to draw tens of thousands. Within two decades, the Jesuits had founded 15 missions in the province of Guayrá alone, spread across more than 100,000 square kilometers. By 1732, the 30 Río de la Plata missions held 141,242 people.

Protection from the encomienda did not mean protection from everything. Beginning in 1628, bandeirante slavers from São Paulo launched devastating raids on the Guayrá missions, seeing in their concentrated populations an easy harvest. The slavers destroyed mission after mission, capturing thousands. Between 1631 and 1638, the Jesuits organized an extraordinary retreat, moving approximately 12,000 surviving mission residents roughly 500 kilometers southwest into Spanish-controlled territory. They were joined by Guaraní refugees from Uruguay and Tapé who had endured the same raids. At the new locations, the Jesuits reestablished 30 reductions. The Guaraní armed themselves -- producing guns and gunpowder within the missions, in defiance of royal orders against arming indigenous people -- and in 1641, a Guaraní militia defeated a bandeirante army of more than 1,500 slavers and Tupi auxiliaries at the Battle of Mbororé.

The mission towns followed a uniform plan. Buildings surrounded a central square: the church and storehouses at one end, long residential blocks forming the other three sides. Each family had its own apartment, though a single veranda and roof might serve a hundred households. The churches were stone or fine wood, with towers, imported Italian and Spanish statuary, and richly carved altars. An inner courtyard housed the priests' quarters, commissary, armory, workshop, and hospital. The plaza itself was grass, cropped by sheep. Within this framework, the Guaraní practiced an astonishing range of trades. Cotton weaving, tanning, carpentry, silversmithing, boat building, printing -- the missions even produced books in Guaraní, illustrated with engravings by indigenous artists. The primary exports were cowhides and yerba mate, initially gathered wild, later cultivated.

In 1767, King Charles III expelled the Jesuits from Spain's American dominions as part of the Bourbon Reforms. Seventy-eight Jesuits departed the missions, leaving behind 89,000 Guaraní in 30 communities. According to historian Sarreal, most Guaraní initially welcomed the change. Spanish authorities made promises to Guaraní leaders, and the leaders of one mission thanked those who "liberated us from the bondage that we lived in as slaves." Within two years, however, the missions' finances collapsed. The Guaraní began leaving, seeking both freedom and wages. A decree in 1800 freed those who remained from their communal labor obligations. By 1840, the former missions were in ruins. Many Guaraní families were impoverished, their communal lands increasingly occupied by mestizo settlers. In 1848, Paraguayan president Carlos Antonio López declared all indigenous people citizens and distributed the last of the mission lands.

Several of the reduction sites survive as towns -- Córdoba, Argentina, the largest, predated the Jesuits as a Spanish settlement and its college became the local university. Many others survive only as ruins, their red sandstone churches rising from subtropical forest. UNESCO has designated multiple mission sites as World Heritage, including six of the Jesuit Missions of Chiquitos in Bolivia and the ruins of Trinidad and Jesús de Tavarangue in Paraguay. The 1986 film The Mission dramatized a version of this history, focusing on the 1750s conflicts, but the real story defies simple framing. The missions shielded the Guaraní from the worst colonial violence while simultaneously imposing European religion and restructuring indigenous life. Two creole languages -- Língua Geral and Nheengatu -- originated in the reductions and survive today, as does Guaraní itself, now one of Paraguay's official languages. What the missions built and what they destroyed remain inseparable.