Crossing the frontier near Charleroi before dawn on 15 June, the French rapidly overran Coalition outposts, securing Napoleon's "central position" between Wellington's and Blücher's armies. He hoped this would prevent them from combining, and he would be able to destroy first the Prussian's army, then Wellington's.

Ney's orders were to secure the crossroads of Quatre Bras, so that he could later swing east and reinforce Napoleon if necessary. Ney found the crossroads of Quatre Bras lightly held by the Prince of Orange, who repelled Ney's initial attacks but was gradually driven back by overwhelming numbers of French troops.

Meanwhile, on 16 June, Napoleon attacked and defeated Blücher's Prussians at the Battle of Ligny using part of the reserve and the right wing of his army. The Prussian centre gave way under heavy French assaults, but the flanks held their ground. The Prussian retreat from Ligny went uninterrupted and seemingly unnoticed by the French.

With the Prussian retreat from Ligny, Wellington's position at Quatre Bras was untenable. The next day he withdrew northwards, to a defensive position he had reconnoitred the previous year—the low ridge of Mont-Saint-Jean, south of the village of Waterloo and the Sonian Forest.

Before leaving Ligny, Napoleon had ordered Grouchy, who commanded the right wing, to follow up the retreating Prussians with 33,000 men. A late start, uncertainty about the direction the Prussians had taken, and the vagueness of the orders given to him, meant that Grouchy was too late to prevent the Prussian army reaching Wavre, from where it could march to support Wellington.

Wellington rose at around 02:00 or 03:00 on 18 June, and wrote letters until dawn. He had earlier written to Blücher confirming that he would give battle at Mont-Saint-Jean if Blücher could provide him with at least one corps; otherwise he would retreat towards Brussels. At a late-night council, Blücher's chief of staff, August Neidhardt von Gneisenau, had been distrustful of Wellington's strategy, but Blücher persuaded him that they should march to join Wellington's army. In the morning Wellington duly received a reply from Blücher, promising to support him with three corps.

From 06:00 Wellington was in the field supervising the deployment of his forces.

Napoleon breakfasted off silver plate at Le Caillou, the house where he had spent the night. When Soult suggested that Grouchy should be recalled to join the main force, Napoleon said, "Just because you have all been beaten by Wellington, you think he's a good general. I tell you Wellington is a bad general, the English are bad troops, and this affair is nothing more than eating breakfast".

Napoleon's seemingly dismissive remark may have been strategic, given his maxim "in war, morale is everything". He had acted similarly in the past, and on the morning of the battle of Waterloo may have been responding to the pessimism and objections of his chief of staff and senior generals.

At Wavre, the Prussian IV Corps under Bülow was designated to lead the march to Waterloo as it was in the best shape, not having been involved in the Battle of Ligny. Although they had not taken casualties, IV Corps had been marching for two days, covering the retreat of the three other corps of the Prussian army from the battlefield of Ligny. They had been posted farthest away from the battlefield, and progress was very slow.

The roads were in poor condition after the night's heavy rain, and Bülow's men had to pass through the congested streets of Wavre and move 88 artillery pieces. Matters were not helped when a fire broke out in Wavre, blocking several streets along Bülow's intended route. As a result, the last part of the corps left at 10:00, six hours after the leading elements had moved out towards Waterloo. Bülow's men were followed to Waterloo first by I Corps and then by II Corps.

At 11:00, Napoleon drafted his general order: Reille's Corps on the left and d'Erlon's Corps to the right were to attack the village of Mont-Saint-Jean and keep abreast of one another. This order assumed Wellington's battle-line was in the village, rather than at the more forward position on the ridge. To enable this, Jerome's division would make an initial attack on Hougoumont, which Napoleon expected would draw in Wellington's reserves, since its loss would threaten his communications with the sea. A grande batterie of the reserve artillery of I, II, and VI Corps was to then bombard the centre of Wellington's position from about 13:00. D'Erlon's corps would then attack Wellington's left, break through, and roll up his line from east to west. In his memoirs, Napoleon wrote that his intention was to separate Wellington's army from the Prussians and drive it back towards the sea.

Historian Andrew Roberts notes that "It is a curious fact about the Battle of Waterloo that no one is absolutely certain when it actually began". Wellington recorded in his dispatches that at "about ten o'clock [Napoleon] commenced a furious attack upon our post at Hougoumont". Other sources state that the attack began around 11:30.The house and its immediate environs were defended by four light companies of Guards, and the wood and park by Hanoverian Jäger and the 1/2nd Nassau.

The initial attack by Bauduin's brigade emptied the wood and park, but was driven back by heavy British artillery fire, and cost Bauduin his life. As the British guns were distracted by a duel with French artillery, a second attack by Soye's brigade and what had been Bauduin's succeeded in reaching the north gate of the house. Sous-Lieutenant Legros, a French officer, broke the gate open with an axe, and some French troops managed to enter the courtyard. The Coldstream Guards and the Scots Guards arrived to support the defence. There was a fierce melee, and the British managed to close the gate on the French troops streaming in. The Frenchmen trapped in the courtyard were all killed. Only a young drummer boy was spared.

Fighting continued around Hougoumont all afternoon. Its surroundings were heavily invested by French light infantry, and coordinated attacks were made against the troops behind Hougoumont. Wellington's army defended the house and the hollow way running north from it. In the afternoon, Napoleon personally ordered the house to be shelled to set it on fire,resulting in the destruction of all but the chapel. Du Plat's brigade of the King's German Legion was brought forward to defend the hollow way, which they had to do without senior officers. Eventually they were relieved by the 71st Highlanders, a British infantry regiment. Adam's brigade was further reinforced by Hugh Halkett's 3rd Hanoverian Brigade, and successfully repulsed further infantry and cavalry attacks sent by Reille. Hougoumont held out until the end of the battle.

A little after 13:00, I Corps' attack began in large columns. Bernard Cornwell writes "[column] suggests an elongated formation with its narrow end aimed like a spear at the enemy line, while in truth it was much more like a brick advancing sideways and d'Erlon's assault was made up of four such bricks, each one a division of French infantry". Each division, with one exception, was drawn up in huge masses, consisting of the eight or nine battalions of which they were formed, deployed, and placed in a column one behind the other, with only five paces interval between the battalions.

The divisions were to advance in echelon from the left at a distance of 400 paces apart—the 2nd Division (Donzelot's) on the right of Bourgeois' brigade, the 3rd Division (Marcognet's) next, and the 4th Division (Durutte's) on the right. They were led by Ney to the assault, each column having a front of about a hundred and sixty to two hundred files.

The leftmost division advanced on the walled farmhouse compound La Haye Sainte. The farmhouse was defended by the King's German Legion. While one French battalion engaged the defenders from the front, the following battalions fanned out to either side and, with the support of several squadrons of cuirassiers, succeeded in isolating the farmhouse. The King's German Legion resolutely defended the farmhouse. Each time the French tried to scale the walls the outnumbered Germans somehow held them off. The Prince of Orange saw that La Haye Sainte had been cut off and tried to reinforce it by sending forward the Hanoverian Lüneburg Battalion in line. Cuirassiers concealed in a fold in the ground caught and destroyed it in minutes and then rode on past La Haye Sainte, almost to the crest of the ridge, where they covered d'Erlon's left flank as his attack developed.

At about 13:15, Napoleon saw the first columns of Prussians around the village of Lasne-Chapelle-Saint-Lambert, 4 to 5 miles (6.4 to 8.0 km) away from his right flank—about three hours march for an army. Napoleon's reaction was to have Marshal Soult send a message to Grouchy telling him to come towards the battlefield and attack the arriving Prussians. Grouchy, however, had been executing Napoleon's previous orders to follow the Prussians "with your sword against his back" towards Wavre, and was by then too far away to reach Waterloo.

Grouchy was advised by his subordinate, Gérard, to "march to the sound of the guns", but stuck to his orders and engaged the Prussian III Corps rear guard under the command of Lieutenant-General Baron von Thielmann at the Battle of Wavre. Moreover, Soult's letter ordering Grouchy to move quickly to join Napoleon and attack Bülow would not actually reach Grouchy until after 20:00.

The 80 guns of Napoleon's grande batterie drew up in the centre. These opened fire at 11:50, according to Lord Hill (commander of the Anglo-allied II Corps), while other sources put the time between noon and 13:30. The grande batterie was too far back to aim accurately, and the only other troops they could see were skirmishers of the regiments of Kempt and Pack, and Perponcher's 2nd Dutch division (the others were employing Wellington's characteristic "reverse slope defence").

The bombardment caused a large number of casualties. Although some projectiles buried themselves in the soft soil, most found their marks on the reverse slope of the ridge. The bombardment forced the cavalry of the Union Brigade (in third line) to move to its left, to reduce their casualty rate.

Uxbridge ordered his two brigades of British heavy cavalry—formed unseen behind the ridge—to charge in support of the hard-pressed infantry. The 1st Brigade, known as the Household Brigade, commanded by Major-General Lord Edward Somerset, consisted of guards regiments: the 1st and 2nd Life Guards, the Royal Horse Guards (the Blues), and the 1st (King's) Dragoon Guards. The 2nd Brigade, also known as the Union Brigade, commanded by Major-General Sir William Ponsonby, was so called as it consisted of an English (the 1st or The Royals), a Scottish (2nd Scots Greys), and an Irish (6th or Inniskilling) regiment of heavy dragoons.

The Household Brigade crossed the crest of the Anglo-allied position and charged downhill. The cuirassiers guarding d'Erlon's left flank were still dispersed, and so were swept over the deeply sunken main road and then routed. Continuing their attack, the squadrons on the left of the Household Brigade then destroyed Aulard's brigade. Despite attempts to recall them, they continued past La Haye Sainte and found themselves at the bottom of the hill on blown horses facing Schmitz's brigade formed in squares.

Napoleon promptly responded by ordering a counter-attack by the cuirassier brigades of Farine and Travers and Jaquinot's two Chevau-léger (lancer) regiments in the I Corps light cavalry division. Disorganized and milling about the bottom of the valley between Hougoumont and La Belle Alliance, the Scots Greys and the rest of the British heavy cavalry were taken by surprise by the countercharge of Milhaud's cuirassiers, joined by lancers from Baron Jaquinot's 1st Cavalry Division.

As Ponsonby tried to rally his men against the French cuirassers, he was attacked by Jaquinot's lancers and captured. A nearby party of Scots Greys saw the capture and attempted to rescue their brigade commander. The French lancer who had captured Ponsonby killed him and then used his lance to kill three of the Scots Greys who had attempted the rescue. By the time Ponsonby died, the momentum had entirely returned in favour of the French. Milhaud's and Jaquinot's cavalrymen drove the Union Brigade from the valley. The result was very heavy losses for the British cavalry. A countercharge, by British light dragoons under Major-General Vandeleur and Dutch–Belgian light dragoons and hussars under Major-General Ghigny on the left wing, and Dutch–Belgian carabiniers under Major-General Trip in the centre, repelled the French cavalry.

A little before 16:00, Ney noted an apparent exodus from Wellington's centre. He mistook the movement of casualties to the rear for the beginnings of a retreat, and sought to exploit it. Following the defeat of d'Erlon's Corps, Ney had few infantry reserves left, as most of the infantry had been committed either to the futile Hougoumont attack or to the defence of the French right. Ney therefore tried to break Wellington's centre with cavalry alone. Initially, Milhaud's reserve cavalry corps of cuirassiers and Lefebvre-Desnoëttes' light cavalry division of the Imperial Guard, some 4,800 sabres, were committed. When these were repulsed, Kellermann's heavy cavalry corps and Guyot's heavy cavalry of the Guard were added to the massed assault, a total of around 9,000 cavalry in 67 squadrons. When Napoleon saw the charge he said it was an hour too soon.

Wellington's infantry responded by forming squares (hollow box-formations four ranks deep). Squares were much smaller than usually depicted in paintings of the battle—a 500-man battalion square would have been no more than 60 feet (18 m) in length on a side. Infantry squares that stood their ground were deadly to cavalry, as cavalry could not engage with soldiers behind a hedge of bayonets, but were themselves vulnerable to fire from the squares. Horses would not charge a square, nor could they be outflanked, but they were vulnerable to artillery or infantry. Wellington ordered his artillery crews to take shelter within the squares as the cavalry approached, and to return to their guns and resume fire as they retreated.

Witnesses in the British infantry recorded as many as 12 assaults, though this probably includes successive waves of the same general attack; the number of general assaults was undoubtedly far fewer. Kellermann, recognising the futility of the attacks, tried to reserve the elite carabinier brigade from joining in, but eventually Ney spotted them and insisted on their involvement.

Eventually it became obvious, even to Ney, that cavalry alone were achieving little. Belatedly, he organised a combined-arms attack, using Bachelu's division and Tissot's regiment of Foy's division from Reille's II Corps (about 6,500 infantrymen) plus those French cavalry that remained in a fit state to fight. This assault was directed along much the same route as the previous heavy cavalry attacks (between Hougoumont and La Haye Sainte). It was halted by a charge of the Household Brigade cavalry led by Uxbridge. The British cavalry were unable, however, to break the French infantry, and fell back with losses from musketry fire.

Although the French cavalry caused few direct casualties to Wellington's centre, artillery fire onto his infantry squares caused many. Wellington's cavalry, except for Sir John Vandeleur's and Sir Hussey Vivian's brigades on the far left, had all been committed to the fight, and had taken significant losses. The situation appeared so desperate that the Cumberland Hussars, the only Hanoverian cavalry regiment present, fled the field spreading alarm all the way to Brussels.

At approximately the same time as Ney's combined-arms assault on the centre-right of Wellington's line, rallied elements of D'Erlon's I Corps, spearheaded by the 13th Légère, renewed the attack on La Haye Sainte and this time were successful, partly because the King's German Legion's ammunition ran out. However, the Germans had held the centre of the battlefield for almost the entire day, and this had stalled the French advance.

With La Haye Sainte captured, Ney then moved skirmishers and horse artillery up towards Wellington's centre. French artillery began to pulverise the infantry squares at short range with canister. The 30th and 73rd Regiments suffered such heavy losses that they had to combine to form a viable square.

The success Napoleon needed to continue his offensive had occurred. Ney was on the verge of breaking the Anglo-allied centre. Along with this artillery fire a multitude of French tirailleurs occupied the dominant positions behind La Haye Sainte and poured an effective fire into the squares. The situation for the Anglo-allies was now so dire that the 33rd Regiment's colours and all of Halkett's brigade's colours were sent to the rear for safety, described by historian Alessandro Barbero as, "... a measure that was without precedent".

Wellington, noticing the slackening of fire from La Haye Sainte, with his staff rode closer to it. French skirmishers appeared around the building and fired on the British command as it struggled to get away through the hedgerow along the road. Many of Wellington's generals and aides were killed or wounded including FitzRoy Somerset, Canning, de Lancey, Alten and Cooke. The situation was now critical and Wellington, trapped in an infantry square and ignorant of events beyond it, was desperate for the arrival of help from the Prussians.

The Prussian IV Corps (Bülow's) was the first to arrive in strength. Bülow's objective was Plancenoit, which the Prussians intended to use as a springboard into the rear of the French positions. Blücher intended to secure his right upon the Châteaux Frichermont using the Bois de Paris road. Blücher and Wellington had been exchanging communications since 10:00 and had agreed to this advance on Frichermont if Wellington's centre was under attack.General Bülow noted that the way to Plancenoit lay open and that the time was 16:30.

At about this time, the Prussian 15th Brigade was sent to link up with the Nassauers of Wellington's left flank in the Frichermont-La Haie area, with the brigade's horse artillery battery and additional brigade artillery deployed to its left in support. Napoleon sent Lobau's corps to stop the rest of Bülow's IV Corps proceeding to Plancenoit. The 15th Brigade threw Lobau's troops out of Frichermont with a determined bayonet charge, then proceeded up the Frichermont heights, battering French Chasseurs with 12-pounder artillery fire, and pushed on to Plancenoit. This sent Lobau's corps into retreat to the Plancenoit area, driving Lobau past the rear of the Armee Du Nord's right flank and directly threatening its only line of retreat. Hiller's 16th Brigade also pushed forward with six battalions against Plancenoit.

Napoleon had dispatched all eight battalions of the Young Guard to reinforce Lobau, who was now seriously pressed. The Young Guard counter-attacked and, after very hard fighting, secured Plancenoit, but were themselves counter-attacked and driven out. Napoleon sent two battalions of the Middle/Old Guard into Plancenoit and after ferocious bayonet fighting—they did not deign to fire their muskets—this force recaptured the village.

Throughout the late afternoon, the Prussian I Corps (Zieten's) had been arriving in greater strength in the area just north of La Haie. General Müffling, the Prussian liaison to Wellington, rode to meet Zieten.

Zieten had by this time brought up the Prussian 1st Brigade (Steinmetz's), but had become concerned at the sight of stragglers and casualties from the Nassau units on Wellington's left and from the Prussian 15th Brigade (Laurens'). These troops appeared to be withdrawing and Zieten, fearing that his own troops would be caught up in a general retreat, was starting to move away from Wellington's flank and towards the Prussian main body near Plancenoit. Zieten had also received a direct order from Blücher to support Bülow, which Zieten obeyed, starting to march to Bülow's aid.

Müffling saw this movement away and persuaded Zieten to support Wellington's left flank. Müffling warned Zieten that "The battle is lost if the corps does not keep on the move and immediately support the English army." Zieten resumed his march to support Wellington directly, and the arrival of his troops allowed Wellington to reinforce his crumbling centre by moving cavalry from his left.

The French were expecting Grouchy to march to their support from Wavre, and when Prussian I Corps (Zieten's) appeared at Waterloo instead of Grouchy, "the shock of disillusionment shattered French morale" and "the sight of Zieten's arrival caused turmoil to rage in Napoleon's army". I Corps proceeded to attack the French troops before Papelotte and by 19:30 the French position was bent into a rough horseshoe shape. The ends of the line were now based on Hougoumont on the left, Plancenoit on the right, and the centre on La Haie.

Meanwhile, with Wellington's centre exposed by the fall of La Haye Sainte and the Plancenoit front temporarily stabilised, Napoleon committed his last reserve, the hitherto-undefeated Imperial Guard infantry. This attack, mounted at around 19:30, was intended to break through Wellington's centre and roll up his line away from the Prussians.

Other troops rallied to support the advance of the Guard. On the left infantry from Reille's corps that was not engaged with Hougoumont and cavalry advanced. On the right all the now rallied elements of D'Érlon's corps once again ascended the ridge and engaged the Anglo-allied line. Of these, Pégot's brigade broke into skirmish order and moved north and west of La Haye Sainte and provided fire support to Ney, once again unhorsed, and Friant's 1st/3rd Grenadiers. The Guards first received fire from some Brunswick battalions, but the return fire of the grenadiers forced them to retire. Next, Colin Halkett's brigade front line consisting of the 30th Foot and 73rd traded fire but they were driven back in confusion into the 33rd and 69th regiments, Halket was shot in the face and seriously wounded and the whole brigade retreated in a mob. Other Anglo-allied troops began to give way as well. A counterattack by the Nassauers and the remains of Kielmansegge's brigade from the Anglo-allied second line, led by the Prince of Orange, was also thrown back and the Prince of Orange was seriously wounded. General Harlet brought up the 4th Grenadiers and the Anglo-allied centre was now in serious danger of breaking.

It was at this critical moment that the Dutch General Chassé engaged the advancing French forces. Chassé's relatively fresh Dutch division was sent against them, led by a battery of Dutch horse-artillery commanded by Captain Krahmer de Bichin. The battery opened a destructive fire into the 1st/3rd Grenadiers' flank. This still did not stop the Guard's advance, so Chassé ordered his first brigade, commanded by Colonel Hendrik Detmers, to charge the outnumbered French with the bayonet; the French grenadiers then faltered and broke. The 4th Grenadiers, seeing their comrades retreat and having suffered heavy casualties themselves, now wheeled right about and retired.

To the left of the 4th Grenadiers were the two squares of the 1st/ and 2nd/3rd Chasseurs who angled further to the west and had suffered more from artillery fire than the grenadiers. But as their advance mounted the ridge they found it apparently abandoned and covered with dead. Suddenly 1,500 British Foot Guards under Maitland who had been lying down to protect themselves from the French artillery rose and devastated them with point-blank volleys. The chasseurs deployed to answer the fire, but some 300 fell from the first volley, including Colonel Mallet and General Michel, and both battalion commanders. A bayonet charge by the Foot Guards then broke the leaderless squares, which fell back onto the following column. The 4th Chasseurs battalion, 800 strong, now came up onto the exposed battalions of British Foot Guards, who lost all cohesion and dashed back up the slope as a disorganized crowd with the chasseurs in pursuit. At the crest the chasseurs came upon the battery that had caused severe casualties on the 1st and 2nd/3rd Chasseurs. They opened fire and swept away the gunners. The left flank of their square now came under fire from a heavy formation of British skirmishers, which the chasseurs drove back. But the skirmishers were replaced by the 52nd Light Infantry (2nd Division), led by John Colborne, which wheeled in line onto the chasseurs' flank and poured a devastating fire into them. The chasseurs returned a very sharp fire which killed or wounded some 150 men of the 52nd. The 52nd then charged, and under this onslaught, the chasseurs broke.

The last of the Guard retreated headlong. A ripple of panic passed through the French lines as the astounding news spread: "La Garde recule. Sauve qui peut!" ("The Guard is retreating. Every man for himself!") Wellington now stood up in Copenhagen's stirrups and waved his hat in the air to signal a general advance. His army rushed forward from the lines and threw themselves upon the retreating French.

The surviving Imperial Guard rallied on their three reserve battalions (some sources say four) just south of La Haye Sainte for a last stand. A charge from Adam's Brigade and the Hanoverian Landwehr Osnabrück Battalion, plus Vivian's and Vandeleur's relatively fresh cavalry brigades to their right, threw them into confusion. Those left in semi-cohesive units retreated towards La Belle Alliance. It was during this retreat that some of the Guards were invited to surrender, eliciting the famous, if apocryphal,retort "La Garde meurt, elle ne se rend pas!" ("The Guard dies, it does not surrender!").

At about the same time of the Imperial Guard attack, the Prussian 5th, 14th, and 16th Brigades were starting to push through Plancenoit, in the third assault of the day. The church was by now on fire, while its graveyard—the French centre of resistance—had corpses strewn about "as if by a whirlwind". Five Guard battalions were deployed in support of the Young Guard, virtually all of which was now committed to the defence, along with remnants of Lobau's corps. The key to the Plancenoit position proved to be the Chantelet woods to the south. Pirch's II Corps had arrived with two brigades and reinforced the attack of IV Corps, advancing through the woods.

The 25th Regiment's musketeer battalions threw the 1/2e Grenadiers (Old Guard) out of the Chantelet woods, outflanking Plancenoit and forcing a retreat. The Old Guard retreated in good order until they met the mass of troops retreating in panic, and became part of that rout. The Prussian IV Corps advanced beyond Plancenoit to find masses of French retreating in disorder from British pursuit. The Prussians were unable to fire for fear of hitting Wellington's units. This was the fifth and final time that Plancenoit changed hands.

French forces not retreating with the Guard were surrounded in their positions and eliminated, neither side asking for nor offering quarter. The French Young Guard Division reported 96 per cent casualties, and two-thirds of Lobau's Corps ceased to exist.

The French right, left, and centre had all now failed. The last cohesive French force consisted of two battalions of the Old Guard stationed around La Belle Alliance; they had been so placed to act as a final reserve and to protect Napoleon in the event of a French retreat. He hoped to rally the French army behind them, but as retreat turned into rout, they too were forced to withdraw, one on either side of La Belle Alliance, in square as protection against Coalition cavalry. Until persuaded that the battle was lost and he should leave, Napoleon commanded the square to the left of the inn. Adam's Brigade charged and forced back this square, while the Prussians engaged the other.

As dusk fell, both squares withdrew in relatively good order, but the French artillery and everything else fell into the hands of the Prussian and Anglo-allied armies. The retreating Guards were surrounded by thousands of fleeing, broken French troops. Coalition cavalry harried the fugitives until about 23:00, with Gneisenau pursuing them as far as Genappe before ordering a halt. There, Napoleon's abandoned carriage was captured, still containing an annotated copy of Machiavelli's The Prince, and diamonds left behind in the rush to escape. These diamonds became part of King Friedrich Wilhelm of Prussia's crown jewels; one Major Keller of the F/15th received the Pour le Mérite with oak leaves for the feat. By this time 78 guns and 2,000 prisoners had also been taken, including more generals.

At 10:30 on 19 June General Grouchy, still following his orders, defeated General Thielemann at Wavre and withdrew in good order — though at the cost of 33,000 French troops that never reached the Waterloo battlefield. Wellington sent his official dispatch describing the battle to England on 19 June 1815; it arrived in London on 21 June 1815 and was published as a London Gazette Extraordinary on 22 June. Wellington, Blücher and other Coalition forces advanced upon Paris.

After his troops fell back, Napoleon fled to Paris following his defeat, arriving at 5:30 am on 21 June. Napoleon wrote to his brother and regent in Paris, Joseph, believing that he could still raise an army to fight back the Anglo-Prussian forces while fleeing from the Waterloo battlefield. Napoleon believed he could rally French supporters to his cause and call upon conscripts to hold off invading forces until General Grouchy's army could reinforce him in Paris. However, following defeat at Waterloo, Napoleon's support from the French public and his own army waned, including by General Ney, who believed that Paris would fall if Napoleon remained in power.

Napoleon announced his second abdication on 24 June 1815. In the final skirmish of the Napoleonic Wars, Marshal Davout, Napoleon's minister of war, was defeated by Blücher at Issy on 3 July 1815. Allegedly, Napoleon tried to escape to North America, but the Royal Navy was blockading French ports to forestall such a move. He finally surrendered to Captain Frederick Maitland of HMS Bellerophon on 15 July. Louis XVIII was restored to the throne of France and Napoleon was exiled to Saint Helena, where he died in 1821. The Treaty of Paris was signed on 20 November 1815.