Though Napoleon Bonaparte's unquenchable thirst for military adventurism eventually cost him both his throne and his freedom during the Napoleonic Wars of the late 18th and early 19th centuries, the French Emperor was not easily defeated even when most of Europe's nations united against him. Two military setbacks on a scale unprecedented in history until then were required before the high tide of Napoleon's success began to ebb towards the final denouement of the Hundred Days and the famous battle of Waterloo.

Napoleon's Russian adventure gutted his veteran army, depriving him of the majority of his finest and most loyal soldiers. Those who remained formed the hard core of his new armies, but the Russian fiasco damaged their health and embittered their previously unquestioning loyalty. Napoleon raised vast new armies, but circumstances compelled him to fill the ranks with raw recruits, whose fighting skills did not equal their undoubted bravery and whose dedication to the Napoleonic cause was shaky, and in many cases due solely to coercion. The tough, experienced, faithful veteran found himself outnumbered by unwilling, sketchily trained amateurs.

These factors set the stage for the second setback, which essentially sealed the fate of Napoleon's empire. The four-day Battle of Leipzig in October 1813, romantically but accurately dubbed the "Battle of the Nations," proved the decisive encounter of the War of the Sixth Coalition and essentially determined the course the Napoleonic Wars took from that moment forward. The resultant collision was the single largest field action of the Napoleonic Wars, dwarfing Waterloo in size, complexity, and overall importance. The Battle of Leipzig was probably the combat which involved the highest concentration of men on a single extended battlefield on the planet up to that point in history, and would not be exceeded until the vast struggles of the First World War almost precisely a century later.