Over at History Day, four military historians reflect on this question. They are Cathal Nolan, Peter H. Wilson, Vanda Wilcox, and Justin Marozzi. Here is a taste of Nolan’s piece:
During the interminable wars among the city states of Renaissance Italy, a contract captain (condottieri) leading a mercenary company had engraved on his breastplate: ‘Enemy of God, Enemy of Piety, Enemy of Pity.’ It is sentiments such as these that led Niccolò Machiavelli to reject the Augustinian and medieval ideal of the ‘just war’, arguing, instead, that there is just war. Machiavelli knew that princes did not act inside a system of law or moral constraint. They lived or went extinct in naked competition for power, cloaked in talk of higher law. Warrior popes sputtered hypocrisies about universal morality, that the laws of God were superior to the will of men. Yet the princes did what they chose. As Machiavelli put it: ‘War is just when it is necessary.’ If he was right, and it is hard as a military historian to say he was not, the only just wars are defensive. No war of aggression can be just, which is why we devote so much effort to saying the other side started it. Quite often, neither side’s cause is just. There is just war.
Read the entire forum here.