its territory to Brazil and Argentina and lost 60% of its population, including 90% of the men. The dictator Lopez was killed in battle and a new government was instituted in alliance with Brazil, which maintained occupation forces in the country until 1876. The last South American war in the 19th century was the War of the Pacific with Bolivia and Peru on one side and Chile on the other. In 1879 the war began with Chilean troops occupying Bolivian ports, followed by Bolivia declaring war on Chile which activated an alliance treaty with Peru. The Bolivians were completely defeated in 1880 and Lima was occupied in 1881. Peace was signed with Peru in 1883 while a truce was signed with Bolivia in 1884. Chile annexed territories of both countries leaving Bolivia landlocked. In the new century, as wars became less violent and less frequent, Brazil entered into a small conflict with Bolivia for the possession of the Acre, which was acquired by Brazil in 1902. In 1917 Brazil declared war on the Central Powers, joined the allied side in the First World War and sent a small fleet to the Mediterranean Sea and some troops to be integrated with the British and French forces in the region. Brazil was the only South American country that participated in the First World War. Later in 1932 Colombia and Peru entered a short armed conflict for territory in the Amazon. In the same year Paraguay declared war on Bolivia for possession of the Chaco, in a conflict that ended three years later with Paraguay's victory. Between 1941 and 1942 Peru and Ecuador fought for territories claimed by both that were annexed by Peru, usurping Ecuador's frontier with Brazil. Also in this period, the first major naval battle of World War II took place in the South Atlantic close to the continental mainland: the Battle of the River Plate, between a British cruiser squadron and a German pocket battleship. The Germans still made numerous attacks on Brazilian ships on the coast, causing Brazil to declare war on the Axis powers in 1942, being the only South American country to fight in this war (and in both World Wars). Brazil sent naval and air forces to combat German and Italian submarines off the continent and throughout the South Atlantic, in addition to sending an expeditionary force to fight in the Italian Campaign. A brief