When some one join the army, if the correct reason is to defend his nation, then he should go to heaven, so long as he obeyed the rule lay down for him. A soldier is not to ask question, but to execute a job assigned to him, be it to kill one, ten, hundred, or thousand of people. Thus the pilots who dropped the two A-bombs have no moral responsibility, but the person who commanded the execution (in this case, the President of USA) is responsible.
The 19 Arabs that flew into buildings etc should go to heaven, but the hand behind which directed the 19 Arab will go to hell. So the thousands of soldiers killing civilians etc in Iraq have not done anything wrong, they are just executing order to defend their nation (as defined by Bush, to fight the terrorists that threaten American liberty etc etc). But the commanders that started to war will answer to God.
Now if a soldier personal opinion is that the Iraq war is wrong, it has nothing to do with defending America, he can do either of the following:
(1) leave the army if he is not under any contract
(2) refuse to go to that war, and go to jail. God will definitely welcome him with open arm in heaven.