Operation Backdoor was a major military initiative by the United States and Colombia during the Brazilian War, in which Allied troops and Republicano guerrillas would sneak through the mountains of Peru to establish a supply chain and then attack Cuiaba from Peru, taking the city by surprise. A major strategic and tactical achievement, the Allies were able to sneak close to 12,000 soldiers and fighters through the Andes, deep in Peruvian territory, with the assistance of the CIA and American Special Forces. On July 18, 1982, in the heart of the local winter, the Allies attacked Cuiaba in the Battle of Cuiaba, and Operation Backdoor's strategic goals were achieved. Through early 1984, the rebel stronghold of Cuiaba was kept alive through secretive weapons and food supply routes through Peru