Those who do not remember the past are condemned to repeat it.

We honor those who took up the sword in the cause of freedom.

I quote George Santayana for this reason.

But, I wonder why others do not.

For if they had,

Why do these happen?

1898-1901 Boxer Rebellion

1899-1902 Boer War

1904-1905 Russo-Japanese War

1910-1920 Mexican Revolution

1912-1913 First and Second Balkan Wars

1914-1918 World War I

1915-1918 Armenian Genocide

1917 Russian Revolution

1918-1921 Russian Civil War

1919-1921 Irish War of Independence

1927-1937 Chinese Civil War

1933-1945 Holocaust

1935-1936 Second Italo-Abyssinian War (aka Second Italo-Ethiopian War)

1936-1939 Spanish Civil War

1939-1945 World War II

1945-1990 Cold War

1946-1949 Chinese Civil War resumes

1946-1954 First Indochina War (aka French Indochina War)

1948 Israel War of Independence (aka Arab-Israeli War)

1950-1953 Korean War

1954-1962 French-Algerian War

1955-1972 First Sudanese Civil War

1956 Suez Crisis

1959 Cuban Revolution

1959-1973 Vietnam War

1967 Six-Day War

1979-1989 Soviet-Afghan War

1980-1988 Iran-Iraq War

1990-1991 Persian Gulf War

1991-1995 Third Balkan War

1994 Rwandan Genocide

(Obviously, not an exhaustive list)