Brazil was under its second civilian-military dictatorship led by Getúlio Vargas, maintaining its official neutrality until 1941, when it allowed US forces to use bases to patrol the South Atlantic. The United States built several airfields on Brazilian soil with the understanding that shortly after the war ended, they would be turned over to Brazil. In the wake of the Japanese attack on Pearl Harbor and the declarations of war of Nazi Germany and Fascist Italy against the US, in January 1942 at the 9th Pan-American Conference held in Rio de Janeiro, Brazil helped to influence other American countries to cut diplomatic relations with Axis Powers. In retaliation, Germany and Italy extended their submarine warfare against them. In the first half of 1942 Axis submarines sank Brazilian merchant ships, and Brazilian naval forces chased and attacked these submarines. When seven merchant ships were sunk by the German Submarine U-507, Vargas decided to make official the state of war against Germany and Italy.