The film opens on Château de Fontainebleau in 1814. Paris is besieged by the Austrians and her allies. Napoleon Bonaparte (Steiger) is urged by his marshals to abdicate but he refuses, defiant. Upon hearing the surrender of his last army under Auguste Marmont he realises that finally all is lost and accepts the abdication pleas of his marshallate. He is banished to Elba, an island in the Mediterranean with a small army of 1,000. Ney (O'Herlihy) calls it an honourable exile.After a tearful farewell to the Old Guard, he is carted away. 10 months later he escapes from Elba and sails back to France. Michel Ney, now under the allegiance of the restored Bourbon king (Welles) is asked to capture him at Grenoble. Ney agrees, eager to earn the respect of the court, who just the day before insulted his "low birth" wife by addressing her as "Madame" despite her title. He declares he'll bring Napoleon back to Paris "in an iron cage", which Louis XVIII says to himself is an exaggerated expression and an overreaction, typical for a militarist.The two men meet on the road from Grenoble. Napoleon, sensing the mood of Ney's troops, goes forward unarmed and asks them if they really want to fire at him.Instead they greet him with cries of "Vive l'Empereur!". Ney is instantly swayed and marches with him and his former soldiers. They return to Paris to a warm welcome by the people. King Louis has fled and the Hundred Days has begun.Napoleon appoints Louis' former Minister of War, Marshal Soult Chief of Staff and he corresponds to the families of the deceased during the war and plans a campaign for the defence of France. He realises he will be attacked but genuinely offers peace to his enemies, who, once more, ignore his communiques and declare war.Prussia and the United Kingdom's forces manoeuvre to counter Napoleon's expected thrust. The armies are not well coordinated and separate, much to the joy of Napoleon, who prepares to place his army between them and defeat one followed by the other.Attention is now drawn to Wellington (Plummer), who attends the Duchess of Richmond's ball, where Picton and other generals are present. One of his soldiers is engaged to her daughter, and the Duchess begs they keep him away from the battlefield so her daughter won't "wear black before she wears white". The young officer declares he will bring back a cuirassier's helmet. Picton overhears and points out that if he ever meets a cuirassier, he'll be lucky to escape with his life, never mind a helmet.The ball is interrupted by General Müffling (John Savident), who announces that Napoleon has crossed the Belgian border at Charleroi, much to Wellington's displeasure. He realises that Napoleon has got between himself and Blücher's Prussians and is on the road to Brussels. Hastily looking at his map, he decides that they will meet at Waterloo.The soldiers are now on their way to Waterloo. Attention then turns to Marschall Blücher (Sergo Zaqariadze) who is seventy-two years of age and yet commands the Prussian army and re-buffs advice by General Gneisenau to retreat. Wellington has done so, but Ney returns to Napoleon to deliver his report on the engagement, which angers Napoleon, who had expected Ney to pursue Wellington, who is now free to choose his own battlefield. Wellington arrives at Waterloo, and asks Blücher to join him in the battle but Müffling wants a new horse to reach him. Wellington is not amused. Before this, an Irish soldier plunders a pig for food. Looting is a capital offence in the British Army, but when Wellington catches him the looter claims the pig got lost and he was trying to find her relatives. Instead of punishing him, Wellington orders the soldier to be promoted to corporal, for he "knows how to defend a helpless position". Wellington then tells de Lancey:I do not know what they'll do to the enemy, but by God, they frighten me!Napoleon is in pain because of trouble with his stomach but when he is asked whether he wants the doctor, he refuses and following a few minutes, he orders his generals out of his outpost after going through tactics. A storm is raging outside with heavy rain pouring down.The day of the battle dawns bright and dry and Napoleon invites his generals to breakfast. They hear the ringing of the local church bell and are initially surprised, until de la Bedoyère mentions that the pastor intends to go ahead with the sermon, despite the looming battle.Napoleon is in a happy mood compared to the night before but now the commander of artillery brings bad news. The rains of the previous night have made it impossible to manoeuvre the French guns. The battle must be delayed until the ground dries. Napoleon, who agrees with Ney that they had fought with muddy boots previously, alone among his generals realises that each delay brings the Prussians closer. He is annoyed and leaves his breakfast to look at the battlefield.The armies move into position opposite each other. Both commanders take turns to ride amongst their troops. Ponsonby and Wellington both marvel at the precision of the French formations, while Wellington refuses permission to an artillery officer to fire long range shot at Napoleon himself. "Leaders of armies have better things to do than fire at each other!"The battle starts shortly after 11.30am with cannon fire from the French. Napoleon then sends a diversionary infantry attack against Wellington's right flank, the Chateau of Hougoumont with the view to stretch the Allied line and to "see the quality of this English aristocrat [Wellington]". Wellington ignores this attack and keeps his line firm.Napoleon sends the corps of d'Erlon up the ridge where Wellington's men are sheltering from the French guns. As they crest the rise they are locked in fierce fighting but are repulsed by British cavalry. Picton's troops plug a gap in the line, but a French musket ball strikes him in the head through his hat, killing him. Meanwhile, Ponsonby's cavalry brigade, including the renowned Scots Greys, have chased the French all the way back to their lines but have become disorganised and their horses blown. Wellington sounds the recall signal, but it is either not heard or is ignored. Napoleon sends his Polish lancers to attack them and Ponsonby is killed after his horse gets stuck in mud.As the battle proceeds, Wellington reorganises his lines, moving them a few yards further back, so they are out of the reach of the French artillery. While Napoleon has taken a short leave from the field, again stricken with stomach pain, Ney sees the movement and believes the British are retreating, and orders the French cavalry to advance on them. The allied units form infantry squares to repel the massed cavalry attacks. A soldier by the name of Tomlinson (Oleg Vidov) wanders from his square and shouts out, "we've never seen each other! How can we kill one another?". He is later seen dead. Richard Hay rallies the faltering squares, urging his men to "think of England" before he is struck by a musket ball and killed, much to the upset of Wellington, a good friend.Napoleon returns and angrily rebukes his marshals for allowing Ney to attack without infantry support. The attacks are repulsed and the French have no fresh troops left, yet Napoleon can see that the cavalry attacks have weakened the Allied line. He determines that the farmhouse of La Haye Sainte is the key to the battlefield and orders its capture. After fierce fighting, a French flag flies above it and Napoleon asks Soult to write a letter to Paris that the battle and the war have been won.Napoleon now sends forward the Imperial Guard to smash the failing allied line. He begins leading the men from the front of the formation himself, but his marshals insist he fall back. Wellington is desperate. He asks for "night... or Blücher!". Wellington orders the forces on his left flank - "every brigade, every battalion" - to abandon their position, to reinforce his center and "put every gun to them".At the same time, the French spot Blücher's Prussian army as they emerge onto the battlefield from the woods, with Blücher warning his men that he will shoot any man he sees with pity for the French. A frustrated Napoleon remarks, "I made one mistake in my life, I should have burnt Berlin".As the French continue their advance over the hill, they realize too late that Maitland's Guards Division is on the reverse of the slope, lying down unseen in the grass, waiting for the French. Wellington calls out to him: "Now, Maitland! Now is your time!". The Guards stand up and at point-blank range fire volley after volley at the French column. The Imperial Guard withdraws, defeated, amid great consternation. Napoleon and Ney attempt to rally the broken army, but to no avail. French morale collapses and a general retreat begins, as Wellington gives the signal for a general advance.The Imperial Guard forms squares in an attempt to ward off the advancing allied forces. Meanwhile, the French retreat has quickly deteriorated into a rout, and Napoleon's marshals physically force the Emperor himself to withdraw from the battlefield.To save their lives, under a flag of truce, a British officer offers surrender terms to Pierre Cambronne (Yevgeny Samoilov), who replies with the famous "mot de Cambronne". In a rare departure from real-life events, the British cavalry move aside to reveal a line of artillery, and proceed to blast the obstinate French square, killing most in it. In reality, as the battle had been won, Blücher and Wellington met to signal the defeat of Napoleon, which is not seen in the film.Wellington is not cheered by his victory. As he surveys the desolate battlefield, which has already attracted looters, he laments, in voice over, that "next to a battle lost, the saddest thing is a battle won".Meanwhile, Napoleon, surrounded by Ney, de la Bedoyère and his marshals, is seen leaving the battlefield in his coach, knowing that this time his days as Emperor really have ended.