This is a good question! Follow up; I'm also curious what kind of treatment he could expect from fellow soldiers?

Is that an accurate description of Upham's character? As I recall, he did his job well through most of the move, gradually earning the respect of the other men - until the final battle, when he was overcome with fear.

To answer that with a yes or no is to acknowledge that combat like what happened in SPR was typical, with one or two men making heroic last stands against numerically superior forces with only a Captain (who is not part of the main unit) as the highest CO with no communication with a headquarters. Had a platoon of paratroopers been ordered to sabotage a bridge and some dick-waving Captain from a different unit showing up uninvited ordered them to rip explosives off the bridge, fight on foot against an armored division to the end, and maybe blow it up if anyone survived, they could rightly tell him to screw and take it up with their superiors.

It'd be likely that Captain Miller would be reprimanded (had he survived) for not just blowing the bridge and regrouping with Private Ryan's unit, but also endangering local operations by not just ensuring the Germans couldn't cross the river. Bridges were desirable, but could always be circumvented. It just would have been nice to have a good strong one available.

They were past enemy lines, and he assumed command of a unit not his own that were under orders to observe and obstruct, like paratroopers were meant to do. By their estimation they had no reinforcements coming. The problem is that movies and American attitudes tend to think of war like an action movie down to a character level, and not a bigger-picture sort of thing, so you never tend to see Allies retreating and sabotaging equipment beneficial to the enemy. See the infamous scene in Battle of the Bulge where Americans wipe out a Tiger II column with oil barrels instead of just sabotaging the depot and rendezvousing with other units.

Then you get into the battle itself, which is pure Hollywood of single soldiers separated far apart mowing down Germans (who don't seem to know what grenades or suppressive fire are) like zombies, which is not realistic. So Upham just trying to survive by not bravely sacrificing himself in a suicide mission when he was a clerk/translator pressed into service wouldn't get him in much trouble.

So summing up my long, pretentious answer, none of this stuff would have really happened, down to the rescue mission and most engagements. Hell, I can't really even imagine the situation of Upham being forced to do ammo running, as anyone would be given what they needed at the start and told to retreat when low or empty.

However, if you were say part of a real engagement and were seen removing yourself from duty, not following orders, or absent from your post, you could be reprimanded or have your actions officially reported.