CUBA IS AN ISLAND of some ten million people, only ninety miles from the United States. Despite its small size, its revolution shook the world. Marching triumphantly into Havana in January 1959, Fidel Castro led a nationalist and then socialist movement that defied the “Colossus of the North,” in a region considered the United States’ sphere of influence. And Castro succeeded even though Cuba was heavily dependent on its northern neighbor for trade and investment.