Modern Europe had its foundations in the end of a war. The Peace of Westphalia (1648) not only concluded decades of religious genocide, which saw Europeans attempt self-extermination, but also heralded the formal recognition of states’ borders and the mutual recognition of sovereignty. The French revolutionary wars, which largely invented conscription and massed formations on battlefields, brought conflict into sharp cultural contrast. Jacques-Louis David’s propagandist painting Napoleon Crossing the Alps depicts the First Consul as a Byronic hero on a white charger, which bears little resemblance to the mule Bonaparte actually rode, led by a guide. Eight years later, across the Pyrenées, the Peninsular War inspired Goya’s The Third of May 1808. French soldiers, faces hidden, aim their muskets at Spanish insurgents, one in angelic white. One hundred and twenty years later, it inspired Picasso’s Guernica.

MacMillan argues that culture, technology, and war are so interdependent that it is difficult to discern which influences which. Of course, some of the greatest literature and cinema was inspired by conflict, from Chaplin’s The Great Dictator to War and Peace and Apocalyse Now. Anti-war bestsellers from Norman Angell’s The Great Illusion (1909) to Smedley Butler’s War Is a Racket (1935) influenced generations, although if one were to read Pride and Prejudice, set in 1813, one would barely know a war was on, if not for the food shortages wrought by the Napoleonic blockade. Austen’s characters prefer ‘tenderly flirting with at least six officers at once’ rather than listening to gruesome sagas of mud and blood. In 1925, the United Kingdom, France, and Germany signed the Locarno Treaties, renouncing war. The following year, Abel Gance was filming his silent epic, Napoléon, in the French countryside. As the red, white, and blue-uniformed actors marched past, grasping their eighteenth-century Charleville muskets, a farmer called out to Gance, ‘Who are we fighting now?’

‘The Italians,’ Gance replied.

‘Ah,’ said the farmer, ‘I knew this Locarno business would come to no good.’

When Napoleon returned from Elba for the Hundred Days, overthrowing the Bourbons, Europe’s sovereigns declared war, not on France but on Napoleon himself. This act, together with the Concert of Europe (1815–1914), marked the beginning of collective security organisations, culminating in the League of Nations (1920–45) and the United Nations. Concert diplomacy ultimately compelled Europeans to formalise international law to limit human-rights abuses on and off the battlefield, exemplified by the First Geneva Convention (1864), which reflected the increasingly horrific toll of organised warfare. The 1929 Geneva Conventions that governed rights in World War II were at least partly respected, even by the Nazis, when it came to prisoners of war, although the Germans routinely ignored Geneva’s strictures when it came to Jewish and Slavic peoples, and hid the Holocaust from international observers. The 1949 Conventions broadened protections further, although it was not until 1977 that Geneva’s Second Additional Protocol appeared, protecting peoples in civil conflicts. Few non-state combatants observe its principles.

‘When the rich wage war it’s the poor who die,’ Jean-Paul Sartre wrote. The gulf between blue bloods’ enthusiasm for war and their citizens’ revilement has contemporary resonance. Before the Great War, Edward VII, Wilhelm II, and Tsar Nicholas II (the son and grandsons of Queen Victoria) discussed a disarmament conference that Nicholas had tentatively suggested. ‘Conference comedy,’ said the Kaiser. ‘Nonsense and rubbish,’ grumbled Edward VII. Their loyal subjects demurred. In the UK, the Women’s Co-operative Guild peaked with 72,000 members in the early 1930s, and supported the Women’s International League for Peace and Freedom , which had chapters in fifty countries. After the war, the Campaign for Nuclear Disarmament and the Women of Greenham Common received global support. In Australia, ‘Save Our Sons’, founded by women, organised protests against Menzies’ conscription as early as 1965. In Germany, Reagan’s deployment of Pershing II nuclear missiles in 1983 fomented the German Green Party, which entered a coalition government with the Social Democratic Party in 1998 and resolutely opposed German participation in the 2003 Iraq War. No German government has supported any international conflict since.

There remains an uneasy juxtaposition between the commemoration and condemnation of conflict. Arrondissements in Paris are saturated with the names of soldiers and battlefields. One can navigate Versailles’ Hall of Mirrors viewing paintings of France’s major battles in chronological order. But attendance by the general public at war museums and commemoration services in Britain, Australia, and Canada decreased markedly from the 1980s, only to experience a remarkable resurgence as Great War anniversaries took place in 2014–18.

Accounting for this revival, Margaret MacMillan argues, ‘Left’ university history departments ‘would prefer not to teach about war at all unless it shows the folly and wickedness of the past’. Conversely, conservatives ‘decry the teaching of history which … concentrates … not enough on great victories’. Brexiter Nigel Farage endorsed Christopher Nolan’s film Dunkirk (2017) as symbolic of ‘Britain standing alone’, ignoring the French troops protecting the British escape, as well as the dozens of allied pilots flying British Spitfires and Hurricanes. The same applies in Australia; narratives emphasise the heroism of the Gallipoli Anzacs, and only a professional pedant would mention that Australians had the worst record among Allied troops for drunkenness, desertion, and syphilis; or that there were much larger British and French armies a few kilometres away.

Generals are always fighting the previous wars. This leads to pushback against new technologies, despite their obvious lethality. Knights on horseback resisted their inevitable obsolescence arising from the vulnerability to, first, longbow men, then gunfire. Italian forces relied explicitly on machine guns during World War I, a weapon their allies thought not quite cricket. French military manuals stressed courage and will power; yet, how could these qualities combat poison gas? US commander John J. Pershing believed the superior riflemanship of American Doughboys on the Western Front in 1918 would overcome the Germans’ defensive trench warfare, despite his French and British allies’ experience to the contrary. The kaiser’s forces responded, ‘regretfully’, as one soldier wrote, by machine-gunning 7,000 Americans each week until Pershing, suffering 120,000 casualties in short order, conceded reluctantly that his allies were right.

From the 1980s, the ‘revolution in military affairs’ signalled the ‘technologization’ of warfare. War had entered the digital age. Officers in Langley, Virginia, could play as important a role as commanders on the battlefield. In the assault on Baghdad in 2003, a geographical information system on a single laptop computer directed bomber crews to their targets with pinpoint accuracy. Drone strikes on Iranian generals and insurgents in Afghanistan are now embedded as military tools of trade. Autonomous robot soldiers are in prototype form. Since the US’s withdrawal from the Anti-Ballistic Missile Treaty in 2001, there are no legal barriers to the militarisation of space. Donald Trump’s much-ridiculed Space Force is merely another platform through which Washington plans to maintain ‘full spectrum dominance’ in military affairs.

MacMillan concludes that we must think about how to avoid war, even as technology overtakes it. But although war between the great powers has become obsolete (there have been no major power conflicts since 1945), killing fields from Syria to Yemen show that bloody civil wars did not disappear with the twentieth century. States still fight proxy wars in other countries, intent upon attaining through force what they cannot obtain lawfully, aided and abetted by politicians and desk generals. ‘War,’ as the Prussian military officer Carl von Clausewitz wrote, ‘is the continuation of politics by other means.’