A book by Margaret MacMillan can be relied upon to be thoroughly researched, well-written and, unusually for historians, to be done so with a lively sense of humour. This study of war through the ages is no exception, despite its sombre theme. Based on MacMillan’s Reith Lectures of 2018, this wider history retains the conversational freshness that made her lectures so lively and accessible.

The key question this book addresses is whether war is something bestial that we, after our ‘long peace’ since 1945, have outgrown. The answer is that such assumptions are possible only if we overlook several proxy wars around the world, some directly involving the West, such as Korea and Vietnam. MacMillan traces the roots of such conflicts as far back as Cain and Abel, dispensing early on with the myth that hunter-gatherer tribal societies, free of modern weaponry and militarism, led peaceful lives. 

Starting with the remains of an iceman from 3300 BC, MacMillan finds convincing evidence, ranging from Aboriginal Australia to the Brazilian rainforest, that Stone Age life could, in Hobbesian terms, be ‘nasty, brutish and short’ thanks to internecine warfare. Unpicking Margaret Mead’s idyllic anthropology of Samoa, MacMillan points out that Mead’s knowledge of the local language was poor, her visit lasted only a few months and she believed uncritically everything the locals told her. Earlier missionaries and sailors recorded Samoans bitterly fighting each other until Western imperialism came along and enforced ‘peace’.

MacMillan’s message is clear: ‘If we do not understand why we fight, we have little hope of avoiding future conflicts.’ She reminds us that the need to make war has evolved with the growth of the nation state and nationalist ideologies and that military expenditure was the largest charge on national budgets until the second half of the 20th century. In the Anglo-French War of 1688-97, Louis XIV spent 74 per cent of his revenues and Britain 75 per cent. Prussia was described as an army that happened to have a state.

MacMillan’s main focus is on modern warfare, whose capacity for destruction multiplied exponentially after the Industrial Revolution. Yet she also credits war for giving us many of the blessings of peacetime, such as jet engines, computers, penicillin and blood transfusions. War as the great leveller heralded important social changes, with votes for women, higher wages for labour, higher taxes for the rich and, in the UK, the National Health Service. 

Turning to the causes of war, MacMillan quotes A.J.P. Taylor’s comment: ‘No war is inevitable until it breaks out.’ She takes us through many of the reasons that fuel its outbreak, ranging from greed for other people’s possessions to propaganda about a nation’s women in danger. Concepts of honour have always been important, whether in Cyrano de Bergerac avenging insults about his nose or Austria punishing Serbia for the assassination of its archduke. Civil wars such as America’s can produce the most savage casualties.

It is instructive how much the rules of warfare have varied across time and cultures. While the Spartan warriors of ancient Greece did not fight on sacred days, the Aztecs had ‘flower wars’ with special costumes and weapons. While 18th-century European generals liked to line their troops in neat, mathematical lines, Napoleon liked to shock his opponents by breaking all the rules.

New technology also played its part, whether through the horse, the chariot, the humble stirrup, the crossbow, gunpowder or, of course, modern weaponry. ‘Modern war’, writes MacMillan, ‘was industrial war, producing armies and navies and eventually air forces on a mass scale.’ When Napoleon invaded Russia, he led an army of 600,000, but in 1944 Stalin could field 6.5 million troops against Germany.    

The 20th century saw civilians and their economic life become legitimate targets for shelling and bombing, with the casualties of 18 million combatants and 50 million civilians in the Second World War. Yet many nationalists, the Nazis most of all, have seen war as sanctifying their nation. MacMillan dispenses with the notion that civilians were less aggressive than soldiers, quoting the otherwise sedate Frau von Bismarck demanding that the French should be shot ‘down to the little babies’.  

A British study during the Second World War found that people in rural areas unaffected by the Blitz were more likely to want German cities bombed than those living in badly hit urban areas. Although most cultures have assumed that war was men’s work, MacMillan reminds us that women have often been its cheerleaders, like the Pankhursts swinging from votes for women to backing conscription for men. It was Tommies in the trenches who fraternised with their German adversaries during the Christmas truces of the First World War and the spontaneous ceasefires to collect the dead.

Looking to the mechanisms for preventing war, the book traces the history of collective security and disarmament from the helpless League of Nations to the marginally more effective United Nations. The Geneva Conventions and our current concept of war crimes were born, MacMillan argues, from the carnage of the US Civil War, while the Nuremberg and Tokyo trials after the Second World War importantly rejected the defence of having simply ‘followed orders’.

But war has also been celebrated by novelists like Thomas Mann and poets and artists ranging from Rupert Brooke and Edward Elgar to Laurence Olivier and Noel Coward. Do such sanitisations of war make it more likely? Pointing to the future risks of war in space, cyberspace and by robots, MacMillan concludes that, by understanding war, we will better understand our own human capacity for both cruelty and kindness, a historian’s optimism that it is hard not to share.

War: How Conflict Shaped Us
Margaret MacMillan
Profile 328pp £20

Zareer Masani is author of Macaulay: Britain’s Liberal Imperialist (Bodley Head, 2013).