Era
1991
20
1952-
15
1992-
15
1961 - 1975
14
1990
12
1961-1975
11
1981-1989
11
2000
11
1946-
10
1981-
10
1981-1993
10
1991-
10
1971-
9
1981-2001
9
1989-
9
1993
9
1993-2001
9
1994
9
1971-1981
8
1986-
8
1991-1995
8
1993-
8
1934-
7
1945-
7
1979-1992
7
1980
7
1945-1989
6
1996
6
2001
6
Persian Gulf War, 1991
6
1979-1990
5
1995
5
1809-1865
4
1960-
4
1990-
4
American Invasion, 1989
4
Civil War, 1861-1865
4
Since 1971
4
Since 1981
4
Since 1991
4
1907-1964
3
1913-1991
3
1952-1998
3
1972-
3
1976
3
1979-
3
1980-2020
3
1982-1994
3
1994-
3
2001-2009
3
more ...