Why Did Napoleon Invade Russia?

In June 1812, Napoleon crossed the Niemen River into Russian territory at the head of the largest army Europe had ever seen — the Grande Armée, over 600,000 men drawn from across his empire and its allies. Within six months, the campaign would collapse into one of the most catastrophic military disasters in history. The invasion wasn't a sudden decision; it was the end point of a five-year alliance that had been unraveling since almost the moment it was signed.

An alliance built on a blockade

The 1807 Treaty of Tilsit had bound Russia to Napoleon's Continental System — the blockade designed to strangle British trade with Europe. For Russia, the arrangement was ruinous: cutting off British markets devastated the Russian economy, which depended heavily on exporting grain and timber to Britain. By the end of 1810, Tsar Alexander I had begun quietly reopening Russian ports to neutral shipping, effectively gutting the blockade from within. Napoleon saw this as a direct betrayal of the Tilsit settlement.

The Polish question

A second, harder grievance concerned Poland. Napoleon had created the Duchy of Warsaw out of formerly Prussian and Austrian territory after Tilsit, and Alexander feared it as the nucleus of a fully restored Polish state — one that would inevitably seek to reclaim territory annexed by Russia in the earlier partitions of Poland. Napoleon's refusal to give Alexander firm guarantees against Polish restoration, combined with disputes over a proposed marriage alliance with the Russian imperial family (which fell through, pushing Napoleon toward marrying Marie-Louise of Austria instead), steadily poisoned the relationship through 1810 and 1811.

From Smolensk to the retreat from Moscow

The invasion itself initially went Napoleon's way tactically, if not strategically: the Russian armies avoided a decisive early battle, retreating and drawing the Grande Armée deep into Russian territory while its supply lines stretched to breaking point. The bloody, inconclusive Battle of Borodino in September 1812 opened the road to Moscow, which Napoleon occupied a week later — only to find the city largely evacuated and burning, with no Russian government left to negotiate surrender terms. With no peace offer coming and winter approaching, Napoleon ordered a retreat in late October. What followed — starvation, disease, temperatures that fell below -30°C, and the disastrous crossing of the Berezina River under Russian attack — destroyed the Grande Armée almost completely. Fewer than 100,000 of the original invasion force made it out of Russia.

Why it mattered

The Russian campaign broke the military and financial core of Napoleon's empire and shattered the myth of his invincibility. Prussia and Austria, previously cowed allies, turned against him within months, launching the War of the Sixth Coalition that would end with his first abdication in 1814. Historians still debate whether the invasion was a strategic necessity to enforce the Continental System or a serious miscalculation of Russian resolve and geography — but its consequences are not in dispute.

Napoleon's own correspondence during the 1812 campaign — orders, dispatches, and letters written from Smolensk, Moscow, and the retreat itself — is plotted on the interactive map, letting you trace the campaign's collapse day by day and place by place.