Even worse, was the fear that a more powerful Argentine Army would launch a surprise attack on the weaker Brazilian Army. To counter this threat, President Getúlio Vargas forged closer links with the United States. Meanwhile, Argentina moved in the opposite direction. During World War II, Brazil was a staunch ally of the United States and sent an expeditionary force to Europe. The United States provided over $100 million in Lend-Lease grants, in return for free rent on air bases used to transport American soldiers and supplies across the Atlantic, and naval bases for anti-submarine operations. In sharp contrast, Argentina was officially neutral and at times favored Germany. 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"). After the sinking of Brazilian merchant ships by German and Italian submarines throughout 1942, popular mobilization forced the Brazilian government to abandon its passiveness and declare war on Germany and Italy in August, 1942. Popular mobilization to make the war declaration effective, with the despatching of Brazilian troops to Europe, continued, but a decision by the Brazilian Government to actually send troops to fight the enemy was only made in January 1943, when Vargas and the U.S President Franklin Delano Roosevelt met in Natal, where the first official agreement was made to create an expeditionary force (BEF). In July 1944 the first BEF group was sent to fight in Italy, and, despite being poorly equipped and trained, it accomplished its main missions. Soon after the war, however, fearing the BEF's popularity and possible political use of the allied victory by some BEF members, the then Brazilian government decided to make demobilization effective, with the BEF still in Italy.