Oswaldo Aranha and the Improvement of Relations 
Two main factors contributed to the growth and expansion of Brazil-American relations: first and foremost was the willingness of the American government to support Brazil as the leading hegemon in South America, and second was Getulio Vargas' need to expand his military, specifically the navy and air force. The most important component of these factors was Oswaldo Aranha Brazilian Ambassador to the United States.
 

Aranha played a key role in early negotiations with the United States with regards to establishing American confidence that theBrazilian government was not pro-German, nor was it implementing policies of crude fascism. Aranha first expressed Brazil's will to heighten relations with the United States as a reaction to "dissatisfied nations in the Americas who wished to expand and who threatened to break the peace and harmony of the continent." Aranha was concerned with Argentina's aggressive support of Nazism, and the continuing turmoil between the two would-be leaders of Latin America. As a response the American military wished to send indiscriminate assistance to Brazil, including an army division to protect the eastern coast of Brazil. Vargas and Aranha only wanted to expand the navy and air force of Brazil, confident that the army, through some of Vargas' proposed domestic expansion policies, would suffice to protect and borders. Indiscriminate aid would also cause suspicion to rise among other South American states. Also, in November of 1938 Vargas disbanded and destroyed the Brazilian branch of the German Nationalist Socialist Party (NSDAP), the party upon which Hitler obtained his leadership. Once this decree was implemented, Nazi plans of extensive subversive acts upon the Brazilian government were uncovered. This increased Vargas' need to expand the military of Brazil. Prior to his November decree, Vargas announced the anti-Nazi decree, "which declared illegal all foreign political organizations." Actions such as these by the president were conducive to American trust of the Vargas regime. Aranha's primary duty was foreign policy writing, and it was his communication with Washington that led to a successful partnership with the United States. It was at the Eighth Inter-American Conference in Lima that Aranha's policy was communicated to the United States, which involved a Brazilian-led pact among the Americas. With Brazil at the helm of a unified Latin America, she could institute the United States as the primary trading partner for all of Latin America. However, with Hitler's invasion of Poland in 1939, military aid became the primary topic of discussion. A world war was in the making, and Brazil was predicted to be of strategic importance to the United States. More importantly, the United States could not be locked out of a fascist Latin America, limiting sea routes to the world through the Pacific and north Atlantic.