Vin Suprynowicz has an absolutely stunning column in the December 10, 2007 Shotgun News which also appeared in the October 28, 2007 Las Vegas Review-Journal. You really need to read the full column. (But I won't even give you a taste, because the Review-Journal has become quite insistent on suits.)
It turns out that G.I. Joe's face was modeled on a real U.S. Marine--a man named Mitchell Paige who received the Congressional Medal of Honor for an exploit that Hollywood would never dared to have portrayed back then--because it would have been too unbelievable. Paige's platoon of 33 men was trying to hold a position on Guadalcanal against two regiments of Japanese soldiers--and by the time morning came, Paige was the only soldier still able to fight. There were at least 2200 dead Japanese soldiers as a result of Paige's unwillingness to give up the fight, moving from machine gun to machine gun to give the illusion that there was more than just one Marine holding the position.
Does anyone find it even slightly surprising that Hollywood would rather "internationalize" a story, forgetting what country they are in?
UPDATE: I had the wrong to link to Vin's column. Fixed.
UPDATE 2: Another reader pointed out that "won" the Congressional Medal of Honor really isn't the right verb; that makes it sound like a contest.