premise: The secretary made the fairly unorthodox decision to choose a site outside Washington because she wanted the ceremony to resonate with the memories of President Truman, under whom NATO was founded. On April 4, 1949, on behalf of the United States, Truman's secretary of state, Dean Acheson, signed the Washington Treaty, which created NATO. Acheson is Albright's favorite predecessor, her aides said.
  Formed in reaction to the threat of the Soviet Union under Stalin, NATO calls for the collective defense of its members and was brought into being with an original 12 members.
  The alliance has expanded three times before, adding Greece and Turkey in 1952, West Germany in 1955 and Spain in 1982. But never before has NATO reached out to its former Eastern-bloc enemies.
   What was one prerequisite for NATO's expansions?
hypothesis: choose a site outside Washington