Royalty and military top brass will this week commemorate the 200th anniversary of the Battle of Waterloo, a great victory which dealt a final, crushing blow to the French Emperor Napoleon.
The battle is seen as one of Britain's greatest military triumphs, ending decades of war and establishing a century of relative peace in Europe.
But it came at a heavy price, and 47,000 men lay dead or wounded after the day's bloodshed.
When the victorious British military commander the Duke of Wellington wrote home on the evening of the victory, he mourned: "My heart is broken by the terrible loss I have sustained in my old friends and companions and my poor soldiers.
"Believe me, nothing except a battle lost can be half so melancholy as a battle won."
Two centuries on and relatives of those who lost their lives at Waterloo will travel back to the field, in present-day Belgium, to lay wreaths in memory of their loved ones.
The Prince of Wales and Duchess of Cornwall will join descendants of Napoleon, Wellington and the other Allied military leader Gebhard Leberecht von Blucher on a tour of the historic battlefield this week.
Napoleon conquered large swathes of Europe after sweeping to power in 1799, and had only been defeated by Allied Forces in 1814 when he was exiled to the Mediterranean island of Elba.
But he escaped the following year, and on June 18 1815 his troops again faced the combined strength of the Allied Forces in the muddy, rain-battered field at Waterloo.
The broadcaster and historian Peter Snow, who has been researching the battle for the past decade, said it was hard to overplay its significance.
He said: "Waterloo is one of the very few battles in human history where you have a hugely decisive and final result that affects the way people live for the next century.
"Waterloo was the final climax of the Napoleonic Wars that had gone on for 25 years.
"Millions of people all over Europe had died and it had to be ended totally and decisively."
He said victory at Waterloo "hammered Europe into a state of pretty effective peace for the next 100 years".
But as Napoleon marched his seasoned troops and heavy artillery into battle, many would have thought him the favourite.
The Duke of Wellington had been caught on the hop and was with his officers at the Duchess of Richmond's ball in Brussels on June 15 1815 - while Napoleon was mobilising his troops for battle to the south.
British troops dashed off to war at 3am the following morning and, with no time to change, many still wore their evening costume as they marched to Waterloo and hid behind the hill's brow waiting for the French to approach.
No-one is entirely sure who fired first, but one soldier recalled that a "canon ball came from Lord knows where" in the morning, and Napoleon's and Wellington's forces were at battle.
Soldiers hacked at each other with swords, and bombarded the enemy with musket and canon fire.
Amid the fire, smoke and deafening din of war many men could not even hear the orders shouted by the officers.
Mr Snow said: "The casualties at Waterloo were huge.
"They were something like 45,000 people dead or wounded in the battle itself, it was a ghastly affair.
"The bloodshed was dreadful.
"You had people hacking at each other, causing dreadful, dreadful wounds."
All day Wellington and Napoleon's forces attacked and counter-attacked, but in the afternoon the Allied Forces enjoyed a major boost when Prussian troops, led by Blucher, arrived and together they defeated the French.
Napoleon abandoned his carriage and fled, his dreams of a new empire in tatters.
He was arrested and exiled to the tiny island of St Helena in the South Atlantic, more than 5,000 miles away from France.
Mr Snow said the victory 200 years ago meant more than the toppling of a French despot, it symbolised the moment Britain became the dominant power in Europe.
He said: "It really was the moment when the British Empire took off and rose to the world's biggest empire in the 19th century."
He said Waterloo "was a decisive and final moment" which changed Europe forever.