Colonel John Cambridge is a doctor whose primary role in the film involves helping—or "helping"—Eldridge cope with life in a war zone. Unfortunately, he doesn't seem to be getting far with his patient, in part because he really doesn't seem to understand the kind of stress Eldridge is experiencing:
CAMBRIDGE: You know, this doesn't have to be a bad time in your life. Going to war is a once-in-a-lifetime experience. It could be fun.
ELDRIDGE: And you know this from your extensive work in the field, right?
CAMBRIDGE: I've done my field duty.
ELDRIDGE: Where was that? Yale?
CAMBRIDGE: Look, you don't want me to come around, I won't come around. These talks are voluntary.
ELDRIDGE: Look, I'm sorry. I appreciate what you're saying, I do. I appreciate our sessions together. But you need to come out from behind the wire and see what we do.
CAMBRIDGE: Well, if the circumstance calls for it, I will. Just like every other soldier.
Eldridge is actually the one with helpful suggestions and actionable advice here, not Cambridge—more time in the field would probably help out the doc in the empathy department. As you can see, Cambridge initially balks at that notion, but later he does actually join the EOD team for an outing.
Sad thing about that, though: on that outing, Cambridge gets blown up by an IED just as the guys are about to head back to camp. So, how's that for irony? He never understands Eldridge's fear of sudden death, but he is the one who ultimately experiences it.