Id say killing for your country goes out the window in real combat, if you were in heavy combat with risk of death, you wouldnt be thinking about how proud your making your countryman, you would be more worried about your own squads survival.
Like andr3az said:
"In my opinion killing in self-defence is only justified if your own life or family/friends/neigbours are in great danger."
Only a fool loves war or someone who has never experienced it.
Notions of loyalty and honor go out the window when you see half your mates face ripped away by a bullet and if you do not have a strong mind for what you may witness in a time of war, it can fuck you up.
If I had to join the army I would. But id be a different person having survived it.