Here is what Wikipedia has to say about it:
After Iwo Jima was declared secured, the Marines estimated there were no more than 300 Japanese left alive in the island’s warren of caves and tunnels. In fact, there were close to 3,000. The Japanese bushido code of honor, coupled with effective propaganda which portrayed American G.I.s as ruthless animals, prevented surrender for many Japanese soldiers. Those who could not bring themselves to commit suicide hid in the caves during the day and came out at night to prowl for provisions. Some did eventually surrender and were surprised that the Americans often received them with compassion, offering water, cigarettes, or coffee. The last of these holdouts on the island, two of Lieutenant Toshihiko Ohno’s men, Yamakage Kufuku and Matsudo Linsoki, lasted six years without being caught and finally surrendered in 1951 (another source gives the date of surrender as January 6, 1949).
So it sounds like they didn’t really think the war was still going on, but more like they though they would have to surrender if they came out and were caught, and they were right. I just thought you might want to know.

A late-night bit of trivia to make me go wander around Wikipedia for a bit. Cool. Thanks Grant!
They held out on Guam until the mid-70’s.
http://en.wikipedia.org/wiki/Japanese_ho…
“The more you know…”
the more you realize that Grant’s an idiot.
What’s your point? It’s too early in the goddamned morning to have to puzzle it out.
Charles, why the hell are you posting as Grant?
Charles would have had some faux-intellectual bullshit about “you can’t help but see the racial divide between the caged Japanese soldier and his American captor”, and then dropped the names of at least 3 fancy writers so he can prove to his professor that he did the required reading.
How often do you rely on Wikipedia for your reporting?!
It must be true – I saw it on Gilligan’s Island.
Another crackerjack post from Grant Brissey.
As late as 2005 there were some Japanese WW II veterans hiding out in the Philippines.