With the start of World War II, in 1939, Vargas maintained neutrality until 1941, when an agreement, proposed by Brazilian foreign relations minister Oswaldo Aranha, was formed between American continental nations to align with any American country in the event of an attack by an external power. Due to this agreement, from Pearl Harbor Brazil's entering the war became just a matter of time. American policy also financed Brazilian iron and steel extraction and placed military bases along the Brazilian North-Northeast coast, headquartered in Natal. With the conquest of Southeast Asia by Japanese troops, Getúlio signed a treaty, the Washington Accords, in 1942, which provisioned the supply of natural rubber from the Amazon to the Allies, resulting in the second rubber boom and the forced migration of many people from the drought-stricken northeast to the heart of Amazônia. These people were known as "Soldados da Borracha" ("rubber soldiers").