The Battle of Waterloo was a battle that was fought between the French army and the British and Prussian armies.

Napoleon was crowned as Emperor of France in 1804, and then launched the successful Napoleonic Wars.  France soon had an empire that stretched from Spain to the Russian border. Defeated at the Battle of Leipzig and elsewhere, he accepted exile on the island of Elba in 1814. In February 1815 he again took control of the French Army. He attacked his enemies in Belgium and was defeated at Waterloo. It was the last battle of the Napoleonic Wars.

History
Napoleon seemed unstoppable until two separate campaigns failed.  He gathered a huge army to invade and conquer Russia in 1812.  His army was caught by the Russian winter and destroyed by the weather and lack of food.  The countries of Eastern Europe, led by Austria and Prussia, began to ally against him, forcing his troops back towards France.  Meanwhile, a small army in Portugal and Spain, led by Arthur Wellesley (later to become Duke of Wellington) began to push Napoleon’s troops out of Spain.

By 1814, Napoleon faced total defeat, with invasions from all sides.  A peace treaty was arranged.  Napoleon would abdicate (give up the throne) and live on a small Mediterranean island called Elba, with a small army.  He was replaced as ruler of France by Louis XVIII, brother of Louis XVI.

The 100 Days
On the island of Elba, Napoleon was not content.  He had been promised money by the new French government, but the money did not come. His wife (an Austrian princess) and his sons were forbidden to visit him.

Messages from France showed that his enemies were quarreling.  He seized his opportunity, going by ship in February 1815 and landing in France again.  His welcome was very mixed.  Many French were tired of war and the death and suffering that it made.  However, others wanted a return to the power and glory of the old days and saw Napoleon as their best hope.

His first days were tense but, by personal leadership and persuasion, Napoleon managed to gain the support of the army. When the king panicked and fled the country, there was little to stop Napoleon returning to Paris and resuming his title of Emperor.

The Waterloo Campaign
What Napoleon needed now was a period of time to organize himself and the French army.  The allies were caught completely by surprise and their only chance to stop him lay with two small armies in Belgium: a British and Dutch army commanded by the Duke of Wellington and a Prussian (German) army commanded by Marshall Blücher.

Napoleon decided on a further gamble. He gathered an army and prepared a surprise attack on Wellington and Blucher, hoping to catch them unprepared. His plan was successful at first and he crossed the Belgian border before Wellington and Blucher could join forces.

Ligny and Quatre Bras
His first battle was at Ligny and, after a fierce day’s fighting, he defeated the Prussian army, forcing it to retreat.  Thinking that Blucher would retreat back to Prussia, Napoleon turned his attention towards Wellington.  There had already been a small battle at Quatre Bras, as Wellington tried to delay the French advance. This had given Wellington enough time to prepare a full defensive position across the road leading to Brussels, near the village of Waterloo.

The French army advanced towards them and set up their camp on a ridge facing the combined British and Dutch (Anglo-Dutch) army.  Heavy rain caused delays and confusion and both armies settled down for the night in the mud to await the dawn and the forthcoming battle.

Napoleon’s army faced the Duke of Wellington’s Anglo-Dutch army near Waterloo on 18th June 1815.  Wellington’s troops were deployed behind a low ridge, partially protecting them from the French massed artillery.

Phase 1 – The Attack on Hougoumont
At  around 11.00 Napoleon ordered his guns to open fire.  French infantry began an attack against the Château of Hougoumont, defended by the British Foot Guards.  This was intended to draw Wellington’s reserves away from the centre, where Napoleon’s main attack would fall.
According to records Hougomont was considered to be a vital key to winning the Battle Of Waterloo.

Phase 2 – The French Infantry Attacks
At 13:30 Napoleon launched an infantry attack against Wellington’s centre.  Men of the King’s German Legion resolutely defended the farm of La Haye Sainte. This disrupted the French attack.  British artillery and musketry succeeded in checking the French assault and the British Household and Union heavy cavalry brigades charged after the wavering Frenchmen.  Elated by their success, the British cavalry pursued their enemy too far and in turn suffered terrible casualties at the hands of the French lancers and light cavalry.

Phase 3 – The French Cavalry Attacks
At 15.00 the Anglo-Dutch army appeared to be retreating after the heavy bombardment they had received all day, so Napoleon's general Marshal Ney led a massed French cavalry attack against Wellington’s centre. However, the British infantry had only been moving back to regroup and tend the wounded, and they were able to form squares to defend themselves from cavalry attack.  The French took terrible casualties as they circled these impregnable formations of infantrymen.

The situation further deteriorated for Napoleon as Blucher's Prussian troops launched an attack at Plancenoit to his rear at 16.30.

Phase 4 – The Prussians begin to increase pressure
By early evening the French attack at Hougoumont, intended as a diversion, was now having the opposite effect.  The French committed more and more troops to the bitter fighting around the château, which was held by only a small force of British Guardsmen.  More French reserves were being sent to meet the Prussian threat to the rear of Napoleon’s army at Plancenoit.  However, the French had at last succeeded in capturing the farm of La Haye Sainte, only a short distance from Wellington’s centre.

Phase 5 – The Attack by the Imperial Guard
At approximately 19.30 Napoleon committed his last reserves in a final effort to obtain victory.  As Prussians arrived to bolster Wellington’s flank, veterans of the French Imperial Guard advanced to 'finish the job'.  The British infantry, exhausted from the continuous cannonade they had received all day, rose to meet them.  The musketry of the British Guards Brigade defeated Napoleon’s finest troops.  They fled, and the whole French army joined them in retreat.  Wellington ordered his entire line to advance and the French were driven from the field.

References

Further reading 
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Battle of Waterloo -Citizendium

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