One of the things I really love in this movie are the rare times that Jack is stubborn and Ennis is flexible. The two examples that come to mind are food things and they happen on the mountain.
The first is when Jack says "no more beans." And suddenly Ennis - who I suspect is not exactly used to giving a rip what others want and has already SAID he doesn't like soup, is suddenly wanting soup -- for jack.
And the other is one of my very favorite moments in the movie for some reason. It's when Ennis loses most of the food to the bear scare and responds to jack's concern about their food supply with "nah, I'd just rather eat beans." There's those couple of beats, and then Jack's "well I won't."
And the next thing you know Ennis is killing a moose (?) for Jack.
These moments show me that Jack is able from early on to take Ennis outside of his normal behavior. That Ennis wants to please jack - which like I said is not, I suspect, his usual m.o.
I think that's a thread through the movie. Even though Jack doesn't ever get Ennis completely, he still has so much power over him.
just random thoughts...