Cold War

Heightened

February 4, 1945
1946
March 1946
1948
April 4, 1949
September 1949
September 1949
February 1950
June 1950
1954
1955
May 1955
October 1956
November 1956
January 1957
August 1957
May 19, 1960
April 1961
April 12, 1961
August 13, 1961
August 17, 1961
February 20, 1962
October 1962
November 1963
July 20, 1969

Neutral

1945
1991

Decreased

March 1947
June 1947
May 12, 1949
1953
July 1953
November 1956
November 1960
1965
1973
1989
September 1989
December 1989
October 3, 1990