While there has been many arguments in favor of supporting a not so stringent attitude towards pacifism and referring to biblical examples of Cornelius and others, I believe that there are very clear scriptural arguments that compel honest Christians to not participate in any national war whatsoever.
Cornelius’ example is brought out to show that Peter did not demand that Cornelius must abandon his military position before accepting his Christian faith and anointing of the Holy Spirit.
1- The record does not show what Cornelius did after his conversion.
2- We have to remember that after receiving the gift of the Holy Spirit and being baptized, it is now the operation of the Holy Spirit and Jesus Christ that would direct the actions of Cornelius from that time onward and not be totally dependant on what Peter or others say.
3- Roman soldiers were not used to fight wars only, but they were also used as police force as well to maintain security and order in the territories that they occupied. Cornelius was probably more likely involved in “policing” duties at the time since there were no wars that are being fought in that area at the time and thus may not have felt compelled to abandon his position. By the way, this same condition applies to the “soldiers” that John the Baptist admonished. Jewish soldiers during Herod’s time were most of the time used as local police and that is why John had asked them to be content and fair and not falsely accuse someone, something that a war fighting soldier would not have to contend with.
In today’s modern states, there are armies which are strictly used in fighting wars, and there are separate forces that act as local police. Such distinction was not that obvious in ancient nations and as a matter of fact, it is not that obvious in some modern third world countries as well.
Self Defense
While it is biblically clear that a person should take necessary precautions and actions in defending himself and his family or household from criminals, robbers, etc, even wild animals, it also shows some remarkable differentiation and limits in this aspect.
1- Jesus had initially instructed his disciples to carry swords in their ministry for the purpose of defending themselves against highway robbers and criminals. However, when the issue was that they are being attacked BECAUSE they are Christians or carrying out the Lord’s work, then the record show that they DID NOT defend themselves. This is in line with Jesus’ own experience the night he was delivered.
2- The experience of the Apostles in Acts and the also the Apostle Paul and most early Christians indicate that when they were attacked because of the Word, they DID NOT defend themselves or their families.
3- What about the case of a malicious army invading the area or the country that a Christian is living in; should not the love of family and neighbor compel a Christian to take arms and fight in a group based self defense?
Again, the biblical precedent of the time of the attack and final destruction of Jerusalem 66-70 AD gives clear indication that Christians fled Jerusalem and the surrounding area and did not participate in any national defense against the invading Roman army which left complete destruction in its quake. Remembering also, that back then they did not have the luxury of the Geneva Convention, war crimes tribunals, etc. Those early Christians had left their countrymen and some presumably close friends and families that had not accepted faith in Jesus to be starved and killed in the hundreds of thousands without lifting a sword in their defense. Does this show that they had no love? Definitely not! For they were simply following their Master’s counsel to abandon the area and also his admonition that “My kingdom is not of this world.” In fact, had they participated in any defense action against the Roman army, they too would have perished. Thus, by following Jesus’ counsel, they have acted most successfully in actually defending themselves.
If there is a national reason to defend ones country against naked aggression, it is the Roman invasion of the Palestine and Judea area which was for no other reason than the gratification of the Roman Empire in its quest for global conquest. Yet, here we find that Christians DID NOT participate in any action to stop, limit or defeat this aggression. In line with this, then sincere Christians would not find it in themselves to lift up arms to fight against national aggression, whether it is Nazism, Communism, Americanism, Islamist or any other form for the simple reason that “Our kingdom is not of this world.”