Srimad Bhagavadgita Sadhaka Sanjivani -Swami Ramsukhdas
"Kill those, who stand already killed, by Me" - this statement of the Lord arouses a doubt, that if someone kills a person it means, that he is killed only by the Lord. Thus, does the murderer incur no sin? The answer is, that no one is authorized to slay others, or to trouble them. He has a right, only to serve others, and give comfort to them. If one had the right to kill others, there would not be any value, of a sanction and prohibition. So, a person, who murders others or tortures them, certainly incurs, sin. But a member of the warrior class, who by giving up pride and selfishness, joins a battle, as sanctioned by scriptures, incurs no sin, because it is his duty.