Paraguay was occupied by the Spanish in 1537 and became a Spanish colony as part of the Viceroyalty of Peru. The area gained its independence, as the Republic of Paraguay, on 14 May 1811. Paraguay was then ruled by a succession of dictators. A devastating war fought from 1865 to 1870 between Paraguay and a coalition of Argentina, Brazil and Uruguay reduced Paraguay’s population from about 600,000 to 233,000. Further severe losses were incurred during the war with Bolivia (1932–35) over territorial claims in the Chaco inspired by the unfounded belief that minerals existed in the territory. A peace treaty by which Paraguay obtained most of the area her troops had conquered was signed in July 1938.