The Battle of Fürth was the final and most decisive battle of the War of the Seventh Coalition. Napoléon Bonaparte, French Emperor and victor at the recent Battle of Waterloo that June, cemented here his legacy as one of the greatest commanders in history by soundly defeating the last grand army of the Coalition in a fierce seven-to-eight hour battle. His victory at Fürth broke all the Coalition's hopes for ever beating him, resulting in the Treaty of Prague (signed that October), which is regarded as having begun the Napoleonic Age. The battle is also significant for being the last battle in which Napoléon ever commanded troops, and also as the bloodiest battle of all the Napoleonic Wars (beating the Battle of Borodino in September 1812) in terms of the total number of men killed and wounded.
Napoléon Bonaparte, in exile since his defeat in the War of the Sixth Coalition in 1814, came out of exile and returned to France in March of the following year. He arrived in Paris on 20 March at the head of a small army that had rallied to his cause once more. Here, he reclaimed the Imperial throne of France and set about organizing a proper army to defeat the Coalition forces that were sure to mobilize in response to his escape from Elba. Sure enough, before he even set foot in the French capital, the members of the Congress of Vienna (Austria, Prussia, Russia, and the United Kingdom) declared Napoléon an outlaw and committed to mobilizing their own armies to once again defeat the Emperor.
By April the French Army had swelled to nearly 200,000 men, roughly 70,000 of whom were placed under the command of the Emperor himself as part of the Army of the North. Expecting the Dutch and Prussians to come south and attempt an attack on Paris – with potential aid from a British landing force – Napoléon invaded Belgium and occupied Brussels, forcing the Dutch to retreat despite only suffering few losses. Constantly reinforcing his army and keeping it well-supplied in enemy territory, Napoléon learned on 7 June that the British, under the command of the Duke of Wellington (commander of the Coalition armies in the Peninsular War and widely regarded as the most capable British general), had landed on the coast and were but a few days from uniting with the Dutch army just to the north. The Prussian army, under Prince Gebhard Leberecht von Blücher, was just thirty miles to the east. Napoléon decided to retreat south – widely criticized at the time – instead of giving battle to the Dutch and British before they could join forces. On 16 June, both Napoléon and Ney scored two unexpected victories against the Prussians and Anglo-allied armies at Ligny and Quatre-Bras (respectively), badly bruising the former and forcing the latter to withdraw and reorganize. With the Prussians out of action, Napoléon gave chase to Wellington and defeated him decisively at Waterloo on 18 June, despite suffering heavy casualties. Here the last battle-ready Prussian troops of the IV Corps were devastated, forcing Blücher to withdraw back to Prussia in defeat. The Emperor then briefly chased the remains of the Dutch army and won a minor victory at the Battle of Wavre two days later, effectively ending all of Napoléon's threats to the north.
In the east, however, Napoléon's two other major enemies, Russia and Austria, had rapidly mobilized their armies once more for battle. Combined they had levied some 400,000 men, though only about 200,000 were properly readied and equipped for campaigning in Germany. Austria's failure to dethrone Joachim Murat in the Neapolitan War (ended on 2 July), despite a humiliating defeat, allowed the Austrians to concentrate their forces against the French. By early September Napoléon had reorganized his forces into an army of 200,000 men, arrayed against a force of about 190,000 Austrians and Russians, under the command of the recently-unretired Archduke Charles. However, to the north loomed a rebuilt and reorganized Prussian army under Blücher of some 74,000 men. The Emperor thus sent Marshals Davout and Soult and their two corps – altogether numbering almost 50,000 men – north on 2 September to fight the Prussians and deal them one last decisive defeat.
On 31 August Napoléon crossed the Rhine and headed east to give battle to Charles and his Coalition army. On 2 September he sent Davout and Soult north, and on 17 September the corps of Marshal Suchet met the Russian vanguard corps under General Raevsky, a veteran commander of Borodino fame, just outside the village of Emskirchen. Despite being outnumbered, Suchet vigorously prosecuted four major attacks against the Russians, who suffered heavy casualties and were forced to withdraw back to the main army. Now with his whole army in Bavaria, Napoléon moved east to attack the Coalition to the north of Nuremberg, who on 22 September moved west to take up positions around Fürth. Though Napoléon would not find out until after the upcoming battle, Davout and Soult had scored a crushing victory against Blücher on 26 September at Diepholz, knocking Prussia out of the war and ensuring that, even if Napoléon suffered a setback against Archduke Charles, he could still win the war.
The French army under Napoléon I was, by late August 1815, restored to much of her former glory. Excepting the II and V Corps under Davout and Soult (of almost 50,000 men and some 110 guns), the Grande Armée was mostly at full strength and in peak condition. The Emperor's four victories in the Netherlands in five days (Ligny, Quatre-Bras, Waterloo, and Wavre) ensured the loyalty of the army in a time of great uncertainty, and convinced many more of the army's veteran soldiers and officers to return to the service of the Emperor and prosecute what would hopefully be his final war. With Masséna fighting the Spanish in Catalonia and with other troops stationed on the French coast to prevent another British invasion, however, Napoléon was unable to bring all of his available manpower to take part in the campaign. Still, his army was formidable, with some of his most distinguished Marshals having rallied to his banner once again.
A simplified explanation of the army's organization on the eve of battle was the following:
Grande Armée: Emperor Napoléon I Bonaparte, 148,000 men
—Imperial Guard, 7,000 men
—I Corps: Marshal Michel Ney, 34,000 men
—III Corps: Marshal Louis-Gabriel Suchet, 27,000 men
—IV Corps: Marshal Guillaume Brune, 20,000 men
—VI Corps: Marshal Jean Rapp, 22,000 men
—IX Corps: Marshal Nicolas Oudinot, 29,000 men
—Reserve Corps (Cavalry): King/Marshal Joachim I Murat, 9,000 men
I Corps, commanded by Marshal Ney, was the largest of the five primary corps of the army, chiefly as a reward for Ney's loyalty (having joined in shortly after the Emperor returned from exile) and for his successes during the Waterloo campaign. The II Corps (25,000 men) under Davout and the V Corps (23,000 men) under Soult were diverted from the campaign on 2 September, stealing from Napoléon any numerical parity he would have had against the Austrians and Russians. Still, however, he was confident in victory: he actually had more guns than the enemy, he led more experienced soldiers and officers, and his army's morale was much higher (many having taken part in the Waterloo campaign; additionally, word had just reached the army of several of Masséna's victories in Spain).
Murat, King of Naples and fresh off his victory over the Austrians in Italy, traveled north with some of his cavalry to once again serve his former Emperor; he was once again placed in command of the entire army's independent cavalry, organized into their own "Reserve Corps".