American Veterans Day
Previously called Armistice Day, commemorating the signing of the armistice that ended the first world war on this day in 1918 at 11am. In the United States it was proclaimed as an annual day of mourning by president Wilson in 1919. The name was then changed to Veterans Day in 1954 to honor all U.S. Veterans, especially those who died in battle.
You may find this summary of just war principles of interest.
It is also noteworthy that the Mayflower Compact was signed on this day in 1620.