How can someone kill another that they don't even know in war and it's called just but to kill another in the street isn't?
You're discussing one of the big questions that have plagued humanity since the beginning of time.
What is the justification for killing? Are we justified in taking the life of the criminal who enters our home uninvited and is perceived as a threat to our life or the lives of our loved ones? Our courts determine that to be self-defense. If we do not defend ourselves and the lives of our loved ones in such a situation we will surely be destroyed. Some consider that to be better than taking a life. I do not believe it to be so.
If a foreign power attempts to take over your nation or threaten the lives of your fellow citizens, are we justified in taking their lives in self defense? If the foreign entity, be it a nation or even a group of religious zealots, attacks and it is their creed to destroy all who do not believe as they, is it better to let them do as they will or do we stop them and defend our people.
Do we have the obligation to defend others who are unable to defend themselves? If I see a mugger threatening the life of an innocent, do I have a moral obligation to stop the mugger using whatever means that are necessary? For me, the answer is yes. I will defend the weak and innocent. If the mugger, in his attempt at retaliation claims to have a revolver in his pocket and claims that he will kill me for defending the weak and innocent, and I have already seen the knife that he is wielding and seen the results of his activities in the bodies that lay at his feet, do I have the right to walk away? Saddam was/is just such an evil man.
When Saddam invaded Kuwait he did so as a first step to take over the entire Middle East. He killed innocents and threatened anyone who got in his way. He had already used WMD's (equivalent to a revolver in the above example) and threatened to use them again. His forces were quickly stopped and in an attempt to be "moderate" the military allowed Saddam to remain in power provided that he surrender and agree to specific terms. He agreed to those terms. He agreed that he would not seek the creation of more WMD's. He agreed to allow random spot inspections to verify that there were no WMD's being manufactured or stored. He agreed to an oil for food program that allowed his people to live without suffering. We were far more concerned about his people than was he. HE had already killed millions of his own people and had established torture camps where men were killed or mutilated and women were tortured and raped.
Instead, what he DID was far from the agreement. He refused to allow the inspections as agreed, which was enough of a reason to rescind the terms of the surrender and re-start the war. He DID pursue a program to generate WMD's, and in fact, when the US and other military forces started to threaten, he promised to USE those WMD's against any attacking military. The very same people who today are calling the President a liar are the same ones who were saying that Saddam HAD those WMD's and were also saber rattling. Kerry said that Saddam had them and had to be removed from power. Kennedy said so too, as did BOTH Clinton's, but in the name of regaining power, it is far more convenient to call the President a liar and vilify those who want to defend OUR interests.
The rest of the world acknowledged that we ALL needed to make our lives safer by removing Saddam, but Germany, France and Russia all wanted to continue to violate the terms of the truce and purchased oil from Saddam, often giving him weapons systems that violated the terms of the agreement.
So the question becomes: "Do we stop such aggression? Do we stop such a person from threatening the world when he pays the families who send a suicide bombers to the U.S. to kill OUR citizens? Do we have ANY obligation to the innocents who were killed by that madman?"
I believe the answer is "Yes", but then, you are entitled to believe anything you wish.