What is a just war? Those who, from St Augustine onwards, have debated the question usually begin with Cicero, the Roman philosopher and statesman, who first attempted a definition in 44 bc.

Cicero’s general understanding of the nature of justice, which was a central duty of those in power, went as follows: ‘Justice instructs us to spare all men, to consider the interests of the whole human race, to give everyone his due, and not to touch property which belongs to others.’