The Just War Theory was fully developed by St Aquinas, who established two sets of criteria for war: Jus ad bellum, "right to wage war” of which are rules that must be consulted before partaking in war so that it may be determined whether entering a war is just and Jus in bello “right conduct in war” which directs how combatants must act within war.
Jus ad bellum, comprises of just cause, legitimate authority, right intention, probability of success, last resort and proportionality. Just cause entails that the reason for going to war needs to be just and therefore cannot condone war in the circumstances of recapture or punishment, of which is in direct contradiction of Augustine’s teachings, however wars can only be caused with the intention protect innocent human life. Wars can only be declared by a legitimate authority such as an elected government or monarch, and therefore cannot be rightly caused by a private authority, as in the case of the East India Company for they could never enter into a just war and would therefore use the British flag to help justify their actions to other nations. The right intention to go to war is a very controversial aspect of the just war theory, it involves force only being used for altruistic purposes and so material gain and boosting economies is always wrong, for this reason the wars in Iraq have been under attack as it is argued that this war was started purely for the resource of oil in the country rather than the giving the Iraqi people liberty from their dictator Saddam Hussein. A similar issue has also been sparked recently in the case of Libya as once again it has been cited the reason for intervention in the country is for the material purpose of gaining oil rather than Libyan liberation from Colonel Gaddaffi. One case, in which this is implemented correctly, was in Cambodia in which the inhumane dictator Pol Pot caused genocide in his country, and so the Vietnamese invaded despite only being tenuously connected to the country and after over throwing Pol Pot left Cambodia in peace. The probability of success is also an issue in a just war, if the war that is started is futile then it can never be just, as in the case of the Second World War when Britain declared war on Germany their chances of success were almost zero considering the treaty between Russia and Germany at the time was still strong. Wars must also only be a last resort, and may only be used after all peaceful and diplomatic alternatives have been seriously explored. It is also just to start a war if negotiations are merely used as a delaying tactic, as in the case of Bosnia where diplomatic intervention merely hindered the right course of justice. Finally, proportionality must be considered before waging a war, a war must be proportionate to its expected evils or harms, this however can be extremely difficult to predict and therefore is problematic in its application.
There are two components of Jus in bello, distinction and military necessity. Distinction or discrimination involves the acts of war being purely directed at enemy combatants and not at civilians caught up in the fighting, and so prohibits bombing civilian area. Military necessity means that wars should be governed by the principle of minimum force and any attack must be intended to help the military defeat the enemy. This principle is used to limit unnecessary death and destruction of non-combatants.
Pacifism an absolutist approach is the complete rejection of the use of any form of physical violence to gain political or social goals, and opposition to violence under any circumstance even in self-defence. Pacifism has its roots in India in the Hindu and Buddhist religions of which taught compassion for all life, whether it be human or not. However pacifism is a great proponent in Christianity; despite the many accounts of war and bloodshed in the Old Testament it too can be seen to condemn violence “Nation will not take up sword against nation, nor will they train for war anymore.” Isaiah 2:4. The teachings of peace were then taken up strongly by Jesus in the New Testament, and are mentioned in the Beatitudes “Blessed are the peace makers, for they shall be called sons of God” Matt 5:9. The idea of vengeance being a justifiable reason to start war is also contradicted in the Sermon on the Mount “You have heard that it was said, 'An eye for an eye, and a tooth for a tooth.' But I tell you, do not resist an evil person. If someone strikes you on the right cheek, turn to him the other also.” Matt. 5:38-39. Jesus then further taught that even in the defence of the innocent violence cannot be used, as Peter came to Jesus’ aid in the Garden of Gethsemane “Put your sword back in its place...for all who draw the sword will die by the sword.” Matt. 26:52.
However it is stated by some that Jesus was not a pacifist, and often cite the Cleansing of the Temple, where Jesus used force to drive the money changers out of God’s house “And Jesus went into the temple of God, and cast out all of them who sold and bought in the temple, and overthrew the tables of the moneychangers” Matt. 21:12. Another passage often quoted “And the one who has no sword must sell his cloak and buy one.” Luke 22:26. Although these appear to undermine pacifism they have also been interpreted as metaphorical or for self-defence and it is often stressed that Jesus has never called for bloodshed.
Some philosophers such as Kant would argue that pacifism eliminates all autonomy as the absolutist nature of pacifism prevents laws being laid down by one’s self and so prevents rationality of which is at the heart of being human. Due to these downfalls in pacifism it can allow for great atrocities being committed such as genocide, if no action can be taken it can be taken advantage of by others who follow other principles easily.