In other words, what if one innocent person chose to die so that 1,000+ others could have a chance to live- Would that person have made a moral or immoral decision?
Assume that other person had a 'good life'. IE- they were not a useless drunk like Carnton in the story.
I don't think it's moral or immoral. It's a rational decision. The soldier makes a rational decision to place his life at risk for his family and country. When he is in a situation where he purposely places himself in the line of fire he is following through on his contract to risk his life. I suppose this could be considered ethical behavior.
Moral imperatives are for everyone. Actions beyond that, that is those which incur death or great harm to self for the sole benefit of others, may still be rational but they fall outside of morality.