Get to know Frank Buckles.  He is perhaps the last living American veteran from World War I.  He got in the army by not telling the whole truth about his age.  The marines and navy didn’t buy his story, but he convinced an army recruiter that Missouri didn’t keep birth certificates; so, he got in.  That was in 1917.  He served throughout World War I.  He would also be a prisoner of war for three years during WWII.  You can read all about him here: http://lcweb2.loc.gov/diglib/vhp-stories/loc.natlib.afc2001001.01070/