The general course of the 2,000 kilometer (1,245 mile) long Argentina–Paraguay boundary was determined following Paraguay’s military loss to Argentina, Brazil and Uruguay in 1870. From west to east the boundary follows the Pilcomayo River until it empties into the Paraguay River and then follows that river until it meets the Paraná River, which it follows upstream until the Brazilian tripoint. The boundary was delimited in four agreements between 1876 and 1945.