French Emperor Napoleon I and his La Grande Armee of over 600,000 French, Polish, Italian, German, Prussian, Austrian, Swiss and Spanish troops, crossed the Nieman River into Russia on 24 June 1812. Napoleon officially wanted to protect Polish lands from Russian invasion but actually wanted to incorporate Russia into his Continental System and prevent Russian trade with Great Britain. Napoleon would eventually capture Moscow, but in accordance with their scorched earth practices, the Russians would burn it to the ground. Without winter quarters and no way to supply himself, Napoleon retreated. Six months after the invasion began, horrific losses in attritional battles with the Czar’s armies, Cossack raiders, lack of supply, and winter weather reduced the La Grande Armee to a shadow of its former self. On 14 December 1812, only 27,000 French troops would recross the Nieman. It was the beginning of the end of the Napoleonic era.