Even without checking Snopes, which is a great site, a careful reading of the tale makes it pretty clear it couldn't be true. If Keeshan was born on June 27, 1927 he would have been 17, four months short of his 18th birthday on the date the Marines took Mount Suribachi in February of 1945. While I suppose someone could have lied about their age, enlisted at 16 and been at Iwo Jima, it strains credibility to figure they would have been a sergeant at age 17.