When Benavides's extended term expired in 1939, Manuel Prado y Ugarteche (1939-45), a Lima banker from a prominent family and son of a former president, won the presidency. He was soon confronted with a border conflict with Ecuador that led to a brief war in 1941. After independence, Ecuador had been left without access to either the Amazon or the region's other major waterway, the Río Marañón, and thus without direct access to the Atlantic Ocean. In an effort to assert its territorial claims in a region near the Río Marañón in the Amazon Basin, Ecuador occupied militarily the town of Zarumilla along its southwestern border with Peru. However, the Peruvian Army (Ejército Peruano-- EP) responded with a lightning victory against the Ecuadorian Army. At subsequent peace negotiations in Rio de Janeiro in 1942, Peru's ownership of most of the contested region was affirmed...

The 1941 war with Ecuador, however, was a major success for Peruvian forces. Peru had established the first paratroop unit in the region and used it to good effect; the first combat in the hemisphere involving airborne troops resulted in the capture of Ecuador's Puerto Bolívar on July 27, 1941. By the end of the month, when military actions ceased, Peru held Ecuador's southernmost province of El Oro and much of the disputed eastern jungle territory that had been part of Ecuador since the 1830s. The Rio Protocol of February 1942 awarded to Peru some 205,000 square kilometers of previously disputed Amazon territory.