John Agar

I doubt if Agar was acting as he was an alcoholic.

Quote from WaynamoJim

When you see Agar in those bit roles in The Undefeated, Chisum and, Big Jake, he looked old, like he was in his 60's. Yet, he was really only around 50 at the time. I really liked him in those early roles in Sands Of Iwo Jima, Fort Apache and, She Wore A Yellow Ribbon and he did another good war movie back then called Breakthrough and, for me, he seemed to disappear from the screen. I don't remember seeing him in anything else till he did a bit part as Dion O'Bannion in St. Valentines Day Massacre. Again, he looked older than his 46 yrs. But, you look on IMDb, and he did alot of roles in both movies and tv. I must have missed all those because I don't remember them.

Agar already looked quite a lot older in "Sands of Iwo Jima" compared to "Fort Apache", even though it was only two years later.