At the end of the 19th century, three linguistic families with ten tribal groups, also known as ethnicities, lived in the Paraguayan Chaco. The central part of the Paraguayan Chaco was inhabited by the Maskoy groups, subdivided into Lengua, Toba, Sanapaná, Angaité, and Guaná. South of the Maskoy lived the Mataco family with the Nivaclé, Choroti, and Macá subdivisions. In the northern part of the Chaco lived two groups from the Zamuco family: the Chamacoco and the Ayoreo. All these peoples relied on hunting and harvesting from the forest for their sustenance, which led them to move regularly in search of food sources.

Between 1927 and 1930, the first groups of farmers from abroad arrived in the Paraguayan Chaco. These settlers belonged to the Mennonite evangelical faith (click here to learn more about Mennonite beliefs). They sought a remote location to preserve their traditions and develop a new life based on agriculture. They settled on lands purchased from the Argentine company Carlos Casado.

Through contact between the settlers and the indigenous people, a motivation arose to preach the gospel to the native population. The Chaco War between Bolivia and Paraguay disrupted the settlers' voluntary isolation and drove the indigenous people away from agricultural settlements. After the war, the indigenous peoples returned and sought assistance from the farmers to settle and abandon their nomadic lifestyle.

The settlers' Council of Churches submitted a request to the Paraguayan government, outlining the intentions and objectives of their missionary plan and seeking government authorization. The government responded favorably, leading to the founding of a missionary association named Luz a los Indígenas ("Light to the Indigenous") on September 17, 1935. The first statutes established four objectives:

1. Teach the indigenous people Christian doctrine according to the Holy Scriptures.
2. Provide education for children and promote Christian ethics among adults.
3. Improve the health of the indigenous population.
4. Foster economic training and agricultural settlement to integrate indigenous people into national life.

In 1936, a mission post was built at what is now known as Yalve Sanga. Over time, the first services emerged, including a medical dispensary, a farm that offered employment, and a school for children. Simultaneously, a communal livestock operation was developed, taking advantage of the open fields surrounding the mission post. The communal work aimed to provide employment for the indigenous people and facilitate their settlement in one place.

Ten years later, the indigenous peoples submitted their first request to organize their lives on their own land. Based on this request, a major colonization project began. The Mennonite Central Committee (MCC) from North America was involved in co-financing the project. The Indigenous Advisory Committee was tasked with purchasing land, primarily funded by international organizations, to settle indigenous peoples. This initiative secured a total of 190,000 hectares of land for indigenous communities and facilitated the establishment of 21 communities.

The MCC requested the formation of a central administration to guide the colonization project. The churches and civil administrations of the three German-Mennonite colonies combined their efforts and agreed in 1961 on an "organization plan for economic, social, and cultural assistance for the indigenous people in the Mennonite colonies of the Chaco." This interethnic cooperation system, formalized in statutes in 1970 and amended in 1976, became known as the Asociación de Servicios de Cooperación Indígena-Mennonita (ASCIM). The entity, along with its name, objectives, and other provisions, was officially recognized with legal status by Executive Decree No. 37.174 on February 10, 1978.

According to its original statutes, the general objective of the ASCIM was "to provide development services so that indigenous families achieve an economic level that protects them from the threat of hunger, disease, and marginalization."

Law No. 904/81 provided a framework for the administrative organization of indigenous communities, enabling them to receive legal status (Article 11). After its recognition, ASCIM began transferring land titles to the established communities at no cost, as stipulated in Article 17. The focus of cooperation shifted to advising the communities so they could acquire the skills needed to farm the land they had received.

In 2016, following analysis and planning, ASCIM adopted a new direction, focusing on promoting the autonomy of indigenous communities.