Is it a sin for a Christian to be a soldier (i.e. someone training to be on the frontlines to kill) in the military?
I have been reading some arguments on both sides of this coin, and both have some weight to them. The main argument from the peaceful side of this coin is that Jesus said "those who live by the sword, will die by the sword" and that first century christians did not serve in the military, except for a few, but they weren't in war at that time. The other side of the coin seperates personal responsibility from state responsibility and says that if you are serving in the military and kill, God holds the head of the state responsible. It also uses the Old Testament wars in many of its arguments.
It seems to me that there is power in not fighting, and that the Bible teaches that we should love our enemies, and not kill others just because a government tells you too. However, it would seem in such an evil world that if we didn't stand up and fight for the protection of others, all Christians would be oppressed. It just keeps flipping back and forth.
Thank you for your question about Christians serving in the military. Probably the three best known books dealing with this subject are:
I could go into the details of the various positions, but I think these books (especially the InterVarsity book) provide a good overview of the arguments on each side.
I might also mention that Tommy Nelson (the pastor of Denton Bible Church in Denton, TX) has put together a 90-minute video on the subject of Christians in the military. It is simply called "God and the Military: Is It Right to Bear Arms?" You can contact him at www.dentonbible.org. Thanks for writing.