What if you could go back in time but you couldn't kill anyone, nor could you come right out and tell anyone what was going to happen. You could only try and win the confidence of say a political leader or military commander and try to influence them in a way that you believed would be a better outcome ex: shorter war, no war, being better prepared etc. etc. You could also only deal with an individual, you couldn't say, just pop into the Oval office and talk to the Pres and all of his advisers, you could only reveal yourself to the Pres him/herself.
I've been interested in Gen. Patton fora long time and he was a very astute geo-strategic thinker (albeit a little scary) and also believed in reincarnation. So in my minds eye, someone who traveled back in time wouldn't be all that unnerving to him.