The 5 Rules of Just War
The 5 rules of Just War were started by St Augustine, who wrote the first two criteria, although Aquinas is credited for writing them clearly and adding the philosophy. Other Christian philosophers debated over the new criteria for the next 500 years until 5 rules were agreed on. Christians are often divided as to whether all 5 rules need to be in place for a war to be 'just', or whether just one or two need to be in place.
"Mankind must put an end to war before war puts an end to mankind."
There must be a reason with a chance of winning, for example, war in defence of aggresion and attack. In World War II, the Allies decided the cause was just, and defended countries from German attack. Some Christians do not think that the Gulf War was just. They claim it was less to do with defence and more to do with oil rights.
The war must be to promote good and overcome evil. Peace and justice must be restored quickly. In World War II, the Allies believed that Hitler himself was evil, aiming for a super race. In the Guld War, most of the Allies believed Saddam Hussein to be evil but realized that the Iraqi people were suffering, especially when used as human shields in military sites.
"The more we sweat in peace, the less we bleed in war."
Proportionality - only enough force should be used as is absolutely necessary to achieve peace. Innocent civilians should not be attacked. In World War I this aim was on the whole upheld, but by World War II civilians were targeted and whole cities bombed. In the Guld War, the use of laser-guided missiles and bombs should have resulted in only military units being bombed. But Hussein rounded up civilians and locked them in these bases, and warned the coalition forces what he was going to do.