This photograph was taken by Lius Sinco for the Los Angeles Times during the battle of Fallouja in November 2004. I don't remember seeing it before but apparently it became an iconic image, an idealised archetype of the US soldier in Iraq.
The man in the picture is Marine Lance Cpl. James Blake Miller.
This photograph brought him a measure of fame. According to Sinco, he was even offered the opportunity to return home and end his tour of duty early. He declined. When he did return to the U.S. he - like so many soldiers - suffered from PTSD. Luis Sinco has been documenting his story.
There are photographs and a two part article on the LA Times website.
Despite the somewhat romanticised observations that pop up now and again through the piece - Sinco is a better photographer than writer I think - it still makes for an interesting read.
Here are the links.
I have some thoughts on what I've read but it's late and I cannot properly formulate them now.