The question references the King James Version (KJV) of the Bible verse Exodus 20:13, which is one of the Ten Commandments. The original Hebrew in this verse says “לא תרצח” (lo ratsach), which literally means “do not immorally kill the innocent.

When the original Hebrew words were translated into English for the KJV in 1611, translators used the word “kill” because at that time in the English language, “kill” was used as we use the word “murder” today. But the English language has changed a lot in 400 years. The word “kill” no longer has the required associations of innocence or immorality. Modern Bible versions now translate this as “You shall not murder.” So Christian soldiers are certainly allowed to “kill” an enemy in war, but never to “murder."