The two men appear to have a fondness of one another based on the short, something commonly found in brothers in arms. Assuming the story starts well before this point, a build up of trust between the two that blurs the lines of loyalty to their country via an unlikely friendship. Perhaps only one of them values this while the other manages to steel his feelings and remain strong to his cause.

Based on this writing, however, they both seemed focused on nothing more than surviving. Something that could come well later into the story as more is revealed about the "common enemy". 

I would recommend an outline as a start. A start to the story as well as a little mid ground to go along with it. (Much like you have.)
If you want to bounce a few ideas back and forth I would happily help. Story boarding can be an arduous task without any outside opinions.



I hope I was helpful, please lemme know watcha' think. Gunther covered most of anything else I could say.