This article considers how Juan Belaieff's experiences in the Caucasus of Russia during the early twentieth century shaped his later work with the Paraguayan military in the Chaco region. His Russian training in both military science and ethnography prepared him for his scouting work in the Chaco, a territory contested by both Bolivia and Paraguay. This work, done with the native population of the Chaco, helped secure victory over the Bolivians during the Chaco War (1932–1935). It also played a key role in his broader project of incorporating the native peoples of the Chaco into the Paraguayan nation-state, a project that drew upon his work on behalf of Russia with the populations of the Caucasus. Significantly, his postwar efforts and ethnographic studies directly led to rights and considerations for Paraguay's indigenous population. Belaieff's work demonstrates how both the Paraguayan military and society (long considered by historians as isolated) were influenced by outside ideas and people.