Since God said we should not kill, is it not a sin when born again Christians in Military services do so?

Although the Bible commands us not to kill (Exodus 20:13Thou shalt not kill.
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1. A murderer is to have his life taken. God told Noah, "Whoso sheddeth man's blood, by man shall his blood be shed: for in the image of God made he man" (Genesis 9:6Whoso sheddeth man's blood, by man shall his blood be shed: for in the image of God made he man.
   See All...). Capital punishment is God's plan in this case.
2. An exception is made for self-protection. Exodus 22:2If a thief be found breaking up, and be smitten that he die, there shall no blood be shed for him.
   See All... states, "If a thief be found breaking up, and be smitten that he die, there shall no blood be shed for him." If you took a life to protect your own life or the lives of others, God accepts that as a proper cause.
3. War is the final exception. About the same time that God was giving the commandment to not kill, He was also numbering "all that are able to go forth to war in Israel" (Numbers 1:3From twenty years old and upward, all that are able to go forth to war in Israel: thou and Aaron shall number them by their armies.
   See All...). The Bible allows for the killing of enemy soldiers in war. Even Jesus spoke of going to war as a natural condition on this earth (Luke 14:31Or what king, going to make war against another king, sitteth not down first, and consulteth whether he be able with ten thousand to meet him that cometh against him with twenty thousand?
   See All...). Paul speaks of a ruler as "a revenger to execute wrath upon him that doeth evil" (Romans 13:4For he is the minister of God to thee for good. But if thou do that which is evil, be afraid; for he beareth not the sword in vain: for he is the minister of God, a revenger to execute wrath upon him that doeth evil.
   See All...). This would include going to war.

However, even though God allows for war and even though Christians are not told that they cannot go to war, that does not mean that Christians have to blindly follow every war without consideration. Peter said, "We ought to obey God rather than men" (Acts 5:29Then Peter and the other apostles answered and said, We ought to obey God rather than men.
See All...). This shows us that there are times when the laws of man go against the law of God. If a Christian knows that a war goes against God, he has the right to refuse to fight it in obedience to a higher power. However, he should be extremely careful in his decision and realize that he will have to pay the consequences no matter what they are. It is not a matter of whether or not we agree with the war. It must go much deeper than that. The war must go against another clear command of God. Only then do we have a right to refuse to fight.