Killing and the Christian
The principle of Mat. 5:38-48 is nonresistance toward all. No killing or wounding or returning evil by a Christian. This is what father God had always intended in the old and new testaments.
There is no evidence in the Bible to indicate that the disciples followed any course but nonresistance even when Paul and the Roman emperors broke into their homes to kill whole families.
Matthew 5:38-48
New King James Version (NKJV)
38 “You have heard that it was said, ‘An eye for an eye and a tooth for a tooth.’[a] 39 But I tell you not to resist an evil person. But whoever slaps you on your right cheek, turn the other to him also. 40 If anyone wants to sue you and take away your tunic, let him have your cloak also. 41 And whoever compels you to go one mile, go with him two. 42 Give to him who asks you, and from him who wants to borrow from you do not turn away.

43 “You have heard that it was said, ‘You shall love your neighbor[b] and hate your enemy.’ 44 But I say to you, love your enemies, bless those who curse you, do good to those who hate you, and pray for those who spitefully use you and persecute you,[c] 45 that you may be sons of your Father in heaven; for He makes His sun rise on the evil and on the good, and sends rain on the just and on the unjust. 46 For if you love those who love you, what reward have you? Do not even the tax collectors do the same? 47 And if you greet your brethren[d] only, what do you do more than others? Do not even the tax collectors[e] do so? 48 Therefore you shall be perfect, just as your Father in heaven is perfect.

Gen. 4:7-8: Cain made the wrong sacrifice which opened the door to sin of hatred, jealousy and finally killing. The sacrifice Christians are to make is in Romans 12:1-2. When they do not do this and yield to the Holy Spirit training as to what this means they will do what is right in their own sight. This often results in operating in expediency (armed guards in churches, killing in 'just' wars) which is operating on the knowledge of good and evil not the Holy Spirit of Life. Note what Jesus says in Mat. 26:52. The disciples surely had a reason to wound and kill to defend each other and Jesus. Also Rev 13:7-10 The antichrist is killing saints and they are to follow nonresistance.

Genesis 4: 23-24 tells of a killing for a wounding possibly to save his own life. He indicates he realizes this was wrong with the statement he makes about Cain in vs 24.

Genesis 9:6-7 is a clear statement on killing. The exception being capital punishment (Old and New testaments) and the OT wars of God's judgments on nations whose cup of iniquity was full. Acts 17:25-27 speaks of all being one blood. God's heart at this time is that men be saved not killed or injured, especially not by carnal Christians defending themselves or others.

King David is a type of Christ and was called by God a man after His own heart. However, Father God told him he could not build the temple because he had shed much blood on the earth in His sight, even though these were nations under judgment in wars God had directed. See I Chronicles 22:7-8 and I Chronicles 28:3 and 1 Kings 5:3.

What is Jesus' view of "just" wars and physical violence? Luke 9:51-56. The disciples did not know what spirit they were of! They thought they had a "good" and Biblical response (see Elisha).
Luke 9:51-56
New King James Version (NKJV)
51 Now it came to pass, when the time had come for Him to be received up, that He steadfastly set His face to go to Jerusalem, 52 and sent messengers before His face. And as they went, they entered a village of the Samaritans, to prepare for Him. 53 But they did not receive Him, because His face was set for the journey to Jerusalem. 54 And when His disciples James and John saw this, they said, “Lord, do You want us to command fire to come down from heaven and consume them, just as Elijah did?”[a]
55 But He turned and rebuked them, and said[b], “You do not know what manner of spirit you are of. 56 For the Son of Man did not come to destroy men’s lives but to save them.”[c] And they went to another village.
Christians who either do not have the Holy Spirit or do not submit to His training in this area end up using 'expediency' or OT justifications for their violence which there is none there either.

Every non believer that a Christian kills ends up in the pit which was the point of what Jesus said in Luke 9:55-56. Then after you wound them, or talk to the ones who are left that are not killed, it makes it hard to tell them about the love of the Lord.

Some justify war by saying the US is a Christian nation. There is no such thing. There are nations with the King's citizens in them being salt and light, not acting like the world and serving its Godless systems, or relying on the expediency of armed guards in churches. see Ezra 8:21-23.

At this point some anecdotal evidence is in order. Nate Saint and those with him who died rather than defend themselves or each other is an example. I will say they were told by leadership not to go and may be the reason for no Divine protection.

On Killing by Lt. Col. Dave Grossman has some good points. After the battle of Gettysburg (the South lost) 100's of rifles were gathered up from the battlefield. Many were double and triple loaded. The reluctance to kill with an individual weapon seemed to be the reason. To cover their reluctance they did not fire but "reloaded". He goes on with more evidence throughout history to support the point, and the ways the military and our society has overcome this.

Also he establishes the killing as one cause of PTSD. His ways to overcome this are junk but his evidence is compelling. This is sowing and reaping for violation of God:s laws. PTSD is overcome by repentance and deliverance. How an airborne ranger and Delta force operator got set free when we had the privilege of ministering deliverance to him is an interesting story.

General S. L. A. Marshall also makes the same point with his unique method of interviewing WW II, Korean War and Vietnam soldiers right after close combat. He interviewed the handful of survivors of Able CO. that hit the Dog Green sector on Omaha Beach. He talked with about 20 men not killed or wounded of over 200. It was the beach that Saving Private Ryan tried to show at the start of the film. He discovered a very high percentage that did not fire their personal weapons in these wars except Vietnam. By then the military had devised training to partially overcome the God given resistance to killing.

In Vietnam one platoon of less than 30 men stood off a force of 200 very determined NVA all night with no artillery and some of the time with no illumination. Near the end, having very little ammo left, knowing they were as good as dead they just all started laughing! Captured NVA later said this really affected their morale. The US troops had the resistance to killing removed and the NVA didn't. This platoon was mostly just a regular bunch of marines that had not even seen "the elephant" yet.

This training is so effective, along with the conditioning to violence that our society provides, that troops will assault immediately when ambushed by a superior well protected force and win! In training the same men thought to themselves, never will I do this! The other force still had that bothersome inhibition.

The US Marines seem to be most open about telling recruits the truth, and perhaps best at it. They tell all their 'boots' that they will make them into trained killers.
Who would Jesus shoot?