Although Trujillo sought to emulate Generalissimo Francisco Franco, he welcomed Spanish Republican refugees following the Spanish Civil War. During the Holocaust in the Second World War, the Dominican Republic took in many Jews fleeing Hitler who had been refused entry by other countries. The Jews settled in Sosua. These decisions arose from a policy of "blanquismo", closely connected with anti-Haitian xenophobia, which sought to add more light-skinned individuals to the Dominican population by promoting immigration from Europe. As part of the Good Neighbor policy, in 1940, the U.S. State Department signed a treaty with Trujillo relinquishing control over the nation's customs. When the Japanese attacked Pearl Harbor Trujillo followed the United States in declaring war on the Axis powers, even though he had openly professed admiration for Hitler and Mussolini. During the Cold War, he maintained close ties to the United States, declaring himself the world's "Number One Anticommunist" and becoming the first Latin American President to sign a Mutual Defense Assistance Agreement with the United States. One tactical asset of the United States in the Cold War was the missile tracking system established across the region, which comprised a series of individual stations in neighboring countries. One of these stations was located in the Dominican Republic, requiring bilateral negotiations to establish the facility, and cooperation to operate it. The ranks of the U.S. military mission in the Dominican Republic swelled, as aircraft trainers and mechanics joined the attachés of the four service branches and their staffs working at the U.S. embassy. The missile tracking station and the military mission were the strongest Cold War ties between the United States and the Dominican Republic, but they became liabilities as the relationship soured.