Memorial Day began as a day to commemorate soldiers killed on both sides in the Civil War. After World War I, it was expanded to honor soldiers killed in all U.S. wars.
Speaking of World War I, this is from The Guns of August:
In August , sitting at a cafe in Aachen, a German scientist said to the American journalist Irwin Cobb: “We Germans are the most industrious, the most earnest, the best educated race in Europe. Russia stands for reaction, England for selfishness and perfidy, France for decadence, Germany for progress. German Kultur will enlighten the world and after this war there will never be another…”
Talk of this kind for years before the war had not increased friendliness for Germany. “We often got on the world’s nerves,” admitted Bethmann-Hollweg, by frequently proclaiming Germany’s right to lead the world. This, he explained, was interpreted as lust for world domination but was really a “boyish and unbalanced ebullience.”
The world somehow failed to see it that way. There was a stridency in the German tone that conveyed more menace than ebullience.