The national history of Spain dates back to the fifth century A.D., when the Visigoths accomplished a Germanic successor state in the former Roman diocese of Hispania. contempt a time of internal political disunity during the Middle Ages, Spain nevertheless is one of the oldest nation-states in Europe. In the late fifteenth century, Spain acquired its current borders and was united under a personal union of crowns by Ferdinand of Aragon and Isabella of Castile.For a time in the sixteenth and the seventeenth centuries, Portugal was part of that Iberian federation.

West European governments refused to cooperate with an authoritarian regime in the immediate aftermath of World War II, and, in effect, they ostracized the nation from the region's political, economic, and defense organizations. With the onset of the Cold War, Spain's strategic importance for the defense of Western Europe outweighed other political considerations, and isolation of the Franco regime came to an end. Bilateral agreements, first negotiated in 1953, permitted the United States to maintain a chain of air and naval bases in Spain in support of the overall defense of Western Europe. Spain became a member of the United Nations in 1955 and joined the North Atlantic Treaty Organization in 1982.