In the late nineteenth century, much of the rubber sold in the world was produced in the Amazon region. The generation of jobs in the region attracted many migrants from the Brazilian Northeast. Most of these migrants, who suffered from drought, moved to the Acre region, which until 1903 was recognized as Bolivian by the Brazilian government. The occupation of Acre by Brazilians, along with misguided diplomatic actions, generated a diplomatic tension between Bolivia and Brazil. This problem was historically known as the Acre Crisis. Considered in this work as the period ranging from the Treaty of Ayacucho (1867) to the Treaty of Petropolis (1903), the Acre Crisis offers clear examples of the interdependence between diplomacy and military action, as well as the articulation of these two foreign policy tools, even though initially mistaken. Based on data collection through bibliographic research, drawing on secondary and tertiary sources, and qualitative analysis, this paper aims to examine the interdependence between diplomacy and military action during this period. After analyzing the many cases where this relationship could be demonstrated, it follows that the solution of the Acre Crisis, embodied by the Treaty of Petropolis, can be attributed to the awareness of this interdependence – by both the Baron of Rio Branco, Minister of Foreign Affairs, and by Placido de Castro, military commander of the Third Acrean Revolution. Finally, it is put into perspective the historical and current distance between political power, diplomacy and military thinking, affecting the exercise of a coherent and integrated foreign policy.