Killing During War:

In the Gospel of John it says, “Greater love has no one than this, that he lay down his life for his friends,” (John 15:13). The provided verses prove that self-defense is indeed allowed. By this logic, in warfare, as long as the opposite side attacks first/creates the conflict, we stand with our vets. If the war is trivial, then we do not stand with the commanding officers/those in charge. This includes vets who by free will, attacked/were hostile first.

War is at times necessary, but it is something that can not be used hastily. "Then said Jesus unto him, Put up again thy sword into his place: for all they that take the sword shall perish with the sword," (Matthew 26:52 KJV).