Jesus never explicitly addresses war in the Bible, so please do not claim that he does. Also, during the first century to century and a half after Jesus’ death and Resurrection Christians thought Christ’s return was imminent. They were preparing for His return so the reality of the need for defense was not a focus. So, the teaching on war did not become “the opposite”, it became defined as it had never been previously.
The Church is also not the war-mongering institution you would like to present it to be.
The Catechism emphasizes “Blessed are the peacemakers”:
The fifth commandment forbids the intentional destruction of human life. Because of the evils and injustices that accompany all war, the Church insistently urges everyone to prayer and to action so that the divine Goodness may free us from the ancient bondage of war.
2308 All citizens and all governments are obliged to work for the avoidance of war.
However, “as long as the danger of war persists and there is no international authority with the necessary competence and power, governments cannot be denied the right of lawful self-defense, once all peace efforts have failed” (Gaudium et Spes 79).
**2309 The strict conditions for legitimate defense by military force require rigorous consideration. The gravity of such a decision makes it subject to rigorous conditions of moral legitimacy. At one and the same time: **
- the damage inflicted by the aggressor on the nation or community of nations must be lasting, grave, and certain;
- all other means of putting an end to it must have been shown to be impractical or ineffective;
- there must be serious prospects of success;
- the use of arms must not produce evils and disorders graver than the evil to be eliminated. The power of modern means of destruction weighs very heavily in evaluating this condition.
The Gospels present Jesus as being generally opposed to violence and encouraging peacemaking,
but do not clearly address the question of war fighting.
The Christian tradition seeks to reconcile Christ’s opposition to violence with the protection of the innocent and the preservation of justice and peace.
Instead of extolling the martial virtues, Jesus declares ‘Blessed are the peacemakers; they shall be called God’s children’ (Mt. 5: 10).
BUT
In Matthew 10: 34, Jesus says: ‘You must not think that I have come to bring peace to the earth; I have come not to bring peace but a sword’.
Christ physically drove the moneychangers from the temple (Jn. 2: 15). And St Paul (Romans, 13: 4) insisted on submission to civil authority, since it came from God. ‘It is not for nothing that they hold the power of the sword, for they are God’s agents of punishment bringing retribution on the offender.’
A leading authority on just war theory, James Turner Johnson, argued that
the early Christian rejection of war-fighting and killing stemmed from their expectation that the Reign of God was imminent and not from pacifism.
The gradual realisation that Jesus’ Second Coming was taking longer than expected led the Christians gradually to focus on more immediate issues, such as military service.
Johnson argues that the sizeable Christian presence in the Roman Army from at least AD 174 indicates that many Christians accepted the legitimacy of military service, and presumably had for some time.
In short, changes in the army, in Roman society and the Christian communities resulted in divergent practices in different parts of the Empire even from early in the second century AD, as the earlier millennial leanings gave way to a realisation that Christians had to contribute to the maintenance of the security of the Empire.
The problem for the Christians was how to maintain the prohibition against killing and violence but also to recognise the need to defend the innocent against violence.
The first major attempt to think through this problem came (well before Constantine) from Clement of Alexandria (AD c.
150-c. 215), whom Johnson regards as ambiguous at times, but who could also be seen as the first Christian just war thinker introducing two elements of what would later become standard just war theory, arguing for the defence of the Empire (just cause), on the authority of the emperor (right authority).
www.compassreview.org/winter03/7.html