Spanish missions in the New World usually pacified sedentary peoples accustomed to the agricultural mode of mission life, prompting many scholars to generalize about mission history. James Saeger now reconsiders the effectiveness of the missions by examining how Guaycuruan peoples of South America's Gran Chaco adapted to them during the eighteenth century. Because the Guaycuruans were hunter-gatherers less suited to an agricultural lifestyle, their attitudes and behaviors can provide new insight about the impact of missions on native peoples. Responding to recent syntheses of the mission system, Saeger proposes that missions in the Gran Chaco did not fit the usual pattern. Through research in colonial documents, he reveals the Guaycuruan perspective on the missions, thereby presenting an alternative view of Guaycuruan history and the development of the mission system. He investigates Guaycuruan social, economic, political, and religious life before the missions and analyzes subsequent changes; he then traces Guaycuruan history into the modern era and offers an assessment of what Catholic missions meant to these peoples.

Saeger's research into Spanish documents is unique for its elicitation of the Indian point of view. He not only reconstructs Guaycuruan life independent of Spanish contact but also shows how these Indians negotiated the conditions under which they would adapt to the mission way of life, thereby retaining much of their independence.

By showing that the Guaycuruans were not as restricted in missions as has been assumed, Saeger demonstrates that there is a distinct difference between the establishment of missions and conquest. The Chaco Mission Frontier helps redefine mission studies by correcting overgeneralization about their role in Latin America.