France declared war on Russia, starting Napoleon's invasion two days later.

The First French Empire declared war on Russian Empire on 22 June [O.S. 10 June] 1812, starting Napoleon's invasion two days later. The declaration of war was presented in a diplomatic note by French ambassador Jacques Lauriston to Russian Foreign Minister Alexander Saltykov in Saint Petersburg. The note, preceded by two years of deteriorating French–Russian relations, stated that the request for passports by Russian ambassador Alexander Kurakin meant a severance of diplomatic relations and that Napoleon "from now on considers himself at war with Russia".

The French invasion of Russia, also known as the Russian campaign, the Second Polish War, and in Russia as the Patriotic War of 1812, was initiated by Napoleon with the aim of compelling the Russian Empire to comply with the continental blockade of the United Kingdom. Widely studied, Napoleon's incursion into Russia stands as a focal point in military history, recognized as among the most devastating military endeavors globally. In a span of fewer than six months, the campaign exacted a staggering toll, claiming the lives of nearly a million soldiers and civilians.