A Japanese soldier in WWII, Hiroo Onoda, held out for 29 years, and refused to quit fighting until he was convinced the war was over… in 1974 (article)

On December 26th, 1944, Onoda was sent to Lubang Island in the Philippines.  His orders from his commanding officers, Major Yoshimi Taniguchi, were simple:

You are absolutely forbidden to die by your own hand. It may take three years, it may take five, but whatever happens, we’ll come back for you. Until then, so long as you have one soldier, you are to continue to lead him. You may have to live on coconuts. If that’s the case, live on coconuts! Under no circumstances are you [to] give up your life voluntarily.

Onoda first saw a leaflet that claimed the war was over in October 1945. When another cell had killed a cow, they found a leaflet left behind by the islanders which read: “The war ended on August 15. Come down from the mountains!”2 But as they sat in the jungle, the leaflet just didn’t seem to make sense, for another cell had just been fired upon a few days ago. If the war were over, why would they still be under attack? No, they decided, the leaflet must be a clever ruse by the Allied propagandists.

Again, the outside world tried to contact the survivors living on the island by dropping leaflets out of a Boeing B-17 near the end of 1945. Printed on these leaflets was the surrender order from General Yamashita of the Fourteenth Area Army.