Solo - in your post where you refernced an article on Pacifism, it mentions the account of the Roman centurion in Matthew 8:5-13. If you do not mind, I would like to address this passage as well.
First - there was no occassion for Christ to comment on the centurion's profession. Rather, Jesus compares his faith with that of the Jews.
The centurion recognizes the authority that Christ has - but nowhere does this passage suggest that the centurion became a disciple of Christ. But let's assume that he did - would he still be able to follow the orders of the Roman Army and be a disciple of Christ?
However, we do have the words of John the Baptist in Luke 3:14. When asked by soldiers what they were to do now, after being baptized, John tells them to 'do violence to no man." This would have made it impossible for them to carry on as soldiers.
Justin Martyr, around 153a.d wrote: "We who were filled with war, and mutual slaughter, and every wickedness, have... changed our warlike weapons, our swords into ploughshares, and our spears into implements of tillage."
In an attack on Christians, the philospher Celsus argued that the Empire would be ruined if everyone did as the nonresistance Christians.
Tertullian wrote: "Shall it be held lawful to amke an occupation of the sword, when the Lord proclaims that he who uses the sword shall perish by the sword? And shall the son of peace take part in the battle when it does not become him even to sue at law? And shall he apply the chain, and the prison, and the torture, and the punishment, who is not the avenger even of his own wrongs?"
Origen, around the year 250 wrote: "We have come in accordance with the counsels of Jesus to cut own our warlike and arrogant swords of argument into ploughshares, and we convert into sickles the spears we formerly used in fighting, For we no longer take 'sword against a nation', not do we learn 'any more to make war,' having become sons of peace for the sake of Jesus, who is our leader."
Lactantius of Bithynia wrote in the early 4th century: "When God forbids us to kill, he not only prohibits us from open violence... but he warns us against the commission of those things which are esteemed lawful among men. Thus it will be neither lawful for a just man to engage in warfare."
Lastly, Maximillian a young Numidian in 295 was brought before the proconsul of Africe for induction - he refused induction and the uniform saying: "I cannot serve as a soldier; I cannot do evil; I am a Christian." "I shall not perish, but when I shall have forsaken this world my sould shall live with Christ my Lord." - He was put to death for refusing induction, at the age of 21.