Les Cent-Jours (The Hundred Days) began on 20 March 1815 when Napoleon returned to Paris at the head of a grass-roots army comprised of soldiers (including the theoretically royalist 5th Infantry Regiment at Grenoble) who had joined him as he came overland through the Alps (now known as the Route Napoléon) and through France after he had escaped from the island of Elba.
Although most of the French population welcomed their once-and-renewed Emperor (except for La Vendée, which revolted and was soundly defeated), the rest of Europe collectively made a great poo in their dungarees. It had taken everyone working collectively to defeat this one Frenchman before Elba, and they were terrified he planned to unite Europe under his banner at their expense. Austria, Britain, Prussia and Russia formed a Seventh Coalition by 25 March and prepared for war.
Fireworks had already begun even before Napoleon strolled down the Champs-Élysées again. Just on the strength of Napoleon’s break-out from Elba, his brother-in-law Marshal Joachim Murat, who had been installed as the king of Napoleonic Kingdom of Naples in 1808, had declared war against the Austrian Empire on 15 March. However, this was a bad move on Murat’s part: “The Austrians were prepared for war. Their suspicions were aroused weeks earlier, when Murat applied for permission to march through Austrian territory to attack the south of France. Austria had reinforced her armies in Lombardy under the command of Bellegarde prior to war being declared.”
Sadly, Murat was no where near the general that Napoleon was, and Napoleon couldn’t come save him from the Austrians because there was only a relatively small army available to him when he first arrived in France. If Murat had waited, the outcome of both the Neapolitan War and Waterloo might have been different.
With no genius to stop them the Austrians ran rough-shod over Murat. After the Austrian victory at the Battle of Tolentino on 3 May, Murat scarpered to Corsica and the Neapolitan forces subsequently signed the Treaty of Casalanza on 20 May. Ferdinand IV was again the King of Naples and sent troops to support the Austrians against the French army.
Although too late for Murat, by the end of May Napoleon was ready for another major war. He had gathered and readied 198,000 troops with 66,000 more in training and had formed L’Armée du Nord (the “Army of the North”) which he would lead in the Waterloo Campaign. On 15 June Napoleon’s forces penetrated into the United Netherlands (modern-day Belgium), where he promptly defeated Prussian Field Marshal, Count Gebhard Leberecht von Blücher at the Battle of Ligny. One of Napoleon’s commanders, Marshal Michel Ney, was less successful, but managed to fight the Duke of Wellington to a draw at the Battle of Quatre Bras on the same day.
The end of Napoleon was nigh, however. On 18 June 1815 the French met the Anglo-Allied troops at the Battle of Waterloo, where he was defeated by the combined efforts of Blucher and Wellington, ending Napoleon’s attempts to reestablish an empire.
Napoleon and his remaining troops retreated to Paris, pursued by the Anglo-Allied army. There, Napoleon abdicated his throne to his four-year-old son Napoleon Francis Joseph Charles Bonaparte on 22 June. The Anglo-Allied forces invaded Paris on 7 August, and the next day King Louis XVIII was restored to the French throne, ending Les Cent-Jours.
Utterly defeated on every front, Napoleon surrendered to Captain Frederick Maitland of the HMS Bellerophon, which transported him to England on 15 July.
From England he was shipped to the island of Saint Helena, where he would spend the rest of his life in exile. He died there of gastric cancer on 5 May 1821, ending the fear that he would ever escape and throw Europe into turmoil again.
Except in alternative, fictive timelines and realities … where he escaped Saint Helena and fled to New Orleans and rose again.