The French call it the battle of Mont St Jean. The Prussians wanted to call it The Victory of La Belle Alliance. Wellington, knowing the English facility with foreign languages, named it Waterloo. Two hundred years ago these quiet villages witnessed a ten-hour frenzy of organised murder which had no precedent in European history.

It’s a small battlefield. You can easily see from side to side: ten square kilometres, nowadays undulating farmland with the same small villages and the same roads – it hasn’t changed much. In 1815 an Anglo-Allied army of 74,000, a French army of 74,000 and a Prussian army of about 30,000 crashed together with swords, lances, muskets and guns to decide the future of Europe. About 40,000 soldiers and 10,000 horses were killed; no-one knows the exact numbers.

Napoleon was sent into exile, Blucher died not long afterwards but Wellington lived to a ripe old age, heaped with honours from a grateful nation. It is Wellington’s account which most of us know today. To his discredit, he eclipsed the contribution of the Prussians, Belgians, Germans and Dutch. In reality, the Prussians’ title for the battle was spot-on: every one of the allies’ forces was essential – take just one of them away and Napoleon would almost certainly have won.

Perhaps Wellington was thinking ‘he who pays the piper calls the tune’. The United Kingdom was the United States of the 18th century and financed the entire war. Its reward was global trade hegemony for another 100 years; a good investment, you might think. But it was actually the Royal Navy which ensured Britain’s mercantile dominance; her land wars were never again as conclusive, glorious or creditable as Waterloo. So the British celebrate it while others don’t.

In some ways Waterloo was a portent of today’s post-war European unity, but not entirely. The English and the French, traditional enemies, seem to have treated each other chivalrously. One French regiment, beating the English back above Hougoumont, were much affected to find one of their own wounded men, bandaged and given a supply of food and water, when they swept the English from the field. But the French and Prussians loathed each other and gave no quarter: tales swirled round the battlefield of prisoners hanged from trees, throats cut… retaliation ensued.

It is tempting to compare the slaughter at Waterloo to Ypres and the Somme. But the differences are more significant. Waterloo had no trenches: soldiers fought each other face to face, hand to hand. The artillery accounted for at least half the deaths and mutilation at Waterloo, but even the best gun-crews could only fire three rounds a minute, and most of those rounds were solid shot. The rest were killed by close-range musket-fire, swords and lances. Dead and wounded men were at once stripped of their valuables by their adversaries, who were very likely to be stripped in their turn.

Waterloo was more like Marathon than Messines. General officers fell like flies. Wellington dined alone at his headquarters on the evening of the 18th June: his staff were dead or in hospital. The men could see their leaders with the naked eye: Wellington’s reputation stems largely from his coolness during the battle (which he later said was touch-and-go). Bounding around on his steeplechaser, he seemed oblivious and impervious. Napoleon too inspired awe; when advised to move away from the cannon-balls which were deluging his position late in the day, he was laconic: ‘The balls have not yet been made which can touch me!’

The ordinary soldiers were forced to face shot and shell imperturbably but were not so lucky. Forty thousand died on the battlefield; thousands more received gruesome injuries and were carried away for amputation and perhaps a slow death from gangrene. They could see the cannon-balls coming, but to duck or break ranks was thought of as worse than death. So they stood stock-still.

It was Napoleon’s surgeon-general, Larrey, who (like Shaka Zulu) understood the importance of rapid treatment for the wounded. Shaka’s answer was a brigade of nurses armed with bactericidal moss; Larrey’s solution was his own design of fast, sprung cart to get the wounded off the battlefield and into the hands of the surgeons. Nevertheless, at Waterloo the French casualties were nearly ten times those of the British.

Waterloo tells us something about the role of morale in determining who wins a battle. The outcome hung in the balance for most of the day. The sight of Prussians on the skyline put new heart into the hard-pressed allies; they repulsed the onslaught of the Imperial Guard – which had never happened before – and the French fell back in dismay. Seizing the opportunity, Wellington threw his entire army into the fray and the French retreat turned into a rout. Many of the French casualties were inflicted during this headlong rush to the south: infantrymen speared in the back by furious Prussian lancers.

Most battlefields need an effort of the imagination. Waterloo doesn’t; compact in space and time, it lets you see exactly what happened, when and why. Hundreds of books have explored the significance of the battle, which can hardly be over-stated. But the central mystery remains… how did Europe’s most accomplished warrior, equipped with the best-motivated army and by far the best artillery support, manage to lose a battle which he thought he would win hands-down? He told his staff that they would be in Brussels for dinner; his Imperial Guard carried no food because they had packed their best uniforms for the victory parade.

Was Napoleon ill? Was he over-confident to the point of rashness? Was he wrong to give responsibility to marshals and generals who, on the most generous estimation, were not up to the job? Was he getting old and tired? No-one knows, but Waterloo was one battle where Napoleon – unlike Wellington – was rarely to be seen: he tried to command the battle from a position well behind the lines. This error would be committed again and again in 1914-1918, with equally disastrous consequences.