On Friday, June 12, Paraguay and Bolivia mark the anniversary of the signing of the 1935 Peace Protocol, which ended hostilities in the Chaco War (1932–1935). The date marks not only the end of the conflict but also the beginning of a long diplomatic and technical process that, after 87 years, resulted in the complete demarcation of the border between the two countries.
The Treaty of Peace, Friendship and Boundaries, signed in Buenos Aires on July 21, 1938, formalized the end of the war and established the foundations for territorial delimitation. Subsequently, the arbitral award of October 10, 1938, issued by the Arbitral College composed of Argentina, Brazil, Chile, the United States, Peru, and Uruguay, technically determined the dividing line in the Chaco.
From that point on, the Paraguayan-Bolivian Joint Boundary Demarcation Commission took on the task of carrying out the work of characterization, demarcation, registration, and border surveillance. Over the decades, topographic surveys were conducted, geographic coordinates were determined, main and secondary boundary markers were erected, international boundary cuts were opened, and the technical complexities imposed by the Chaco geography were resolved.
Among the most significant markers are the 10 main boundary pillars erected along the border: Esmeralda (tripoint between Argentina, Bolivia, and Paraguay), 10 de Octubre, Sargento Rodríguez, Gabino Mendoza, Coronel Cabrera, Palmar de las Islas, Coronel Sánchez, Cerro Chovoreca, Cerrito Jara, and 12 de Junio, at the confluence of the Río Negro (tripoint between Brazil, Bolivia, and Paraguay). Witness markers were also installed on each bank of the Río Negro, where the boundary point is georeferenced.
An important milestone in this process was the resolution of the controversy over Vertex VIII of Cerro Chovoreca in 1969, through the arbitration of Argentine General Gonzalo Gómez, an example of the use of peaceful mechanisms to resolve border disputes.
On June 12, 2009, Paraguay and Bolivia signed in Buenos Aires the Additional Protocol to the Treaty of Peace, Friendship and Boundaries, approved in Paraguay by Law No. 4176/2010. The agreement allowed for the formation of a new Paraguayan-Bolivian Joint Boundary Demarcation Commission, composed of national commissions linked to the foreign ministries of both countries, with Argentina withdrawing from the technical work.
This new period of cooperation strengthened binational work with geodetic updates through new technologies, installation and maintenance of border markers, cleaning and reopening of international boundary cuts, as well as the implementation of complementary mechanisms such as the non aedificandi zone (established by exchange of notes on May 31, 2011), intended to preserve the visibility and functionality of the international boundary.
The process reached its culminating point in December 2025, during the government of Santiago Peña, with the formal completion of the total demarcation of the international border between Paraguay and Bolivia. The technical fieldwork, including bathymetry and characterization of the fluvial stretch of the Río Negro, in the Bahía Negra area (Alto Paraguay department), made it possible to complete the 742 kilometers of shared boundary — 704 kilometers of dry border and 38 kilometers of river border.
With this achievement, Paraguay and Bolivia fully consolidated their common border and have now become the only countries in South America with fully demarcated borders, standing as an example of binational cooperation, technical rigor, and commitment to the peaceful resolution of disputes.