Memorial Day had its origin as Decoration Day following the Civil War, but it only became an official federal holiday to honor those who lost their lives while serving in the armed forces of the United States in 1971.
Memorial Day is also an occasion to associate those who died with the just causes for which the United States was willing to go to war. World War I, World War II, Korea, and Vietnam were conflicts where freedom was clearly at stake. The post 9/11 engagements in Afghanistan, Iraq and Syria remain a bit more complicated, being associated with responses to horrific abuse of power and to transnational radical Islamist terrorism.