Chaco War

(1932–35), costly conflict between Bolivia and Paraguay. Hostile incidents began as early as 1928 over the Chaco Boreal, a wilderness region of about 100,000 square miles (259,000 square km) north of the Pilcomayo River and west of the Paraguay River that forms part of the Gran Chaco. The conflict stemmed from the outcome of the War of the Pacific (1879–84), in which Chile defeated Bolivia and annexed that nation's