Veteran's Day is on November 11 for a reason. Shooting in The Great War, The War to End All Wars, The Big One, WWI came to a halt through an armistice agreement at eleven minutes after the eleventh hour on the eleventh day of the eleventh month 1918. The slaughter and death was so horrific both sides wanted a memorable moment to halt the killing. The actual end of the war actually came on June 28, 1919 with the signing of the Treaty of Versailles. One could make the argument that WWII began on June 29, 1919.
WWI has largely become forgotten. It was overshadowed by the world war that erupted a generation later. I'm not sure that the First World War was more gruesome or horrific for the combatants than wars that came and went before or after. The new ways modern man invented to kill one another, the scale of death to civilians and combatants alike was unprecedented. It is not exaggerating to state that a significant amount of the young men of a generation were wiped out. Study The Great War and you can understand why the French passed when the Germans came calling at the start of the Second World War. It is also no way denegrating the service of the American soldiers, sailors, and marines when I say their contribution was material, important, but minuscule compared to the rest of the nations involved.
If you have not studied WWI, I suggest you do some research. My own investigations over the years have barely scratched the surface. If you are not into history books, Dan Carlin's Hardcore History podcast has an excellent series that covers the war in an entertaining and educational manner. His description of the opening days to the horrors of the end give a good flavor to the war. Barbara Tuchman's "The Guns of August" is one of the first histories I read of the war more than 30 years ago. A good historical fiction account is "To the Last Man"by Jeff Shaara.