Napoleon's Invasion of Russia

As the Russians withdrew, they employed a scorched-earth tactic, and although the French army reached Moscow, it did not obtain the decisive result it had expected. During the retreat, the army suffered enormous losses owing to harsh winter conditions, famine, disease, and constant attacks. The campaign ended in catastrophe and became a turning point in the decline of Napoleon's power; it also altered the balance of alliances in Europe.

Source: Wikipedia