Hated by its neighbors, and having to hold down various malcontents at home as well as to stare down so many enemies abroad, the French state stands in need of brilliant deeds and consequently of war. It must be the foremost of states or it must perish.

--Napoleon Bonaparte

The militant crusade of the French Revolution against the monarchies of Europe was channeled by Napoleon to serve his own insatiable ambition of empire. From 1805 until his final downfall in 1815, Napoleon embarked on a series of wars in which his adversaries often proved no match. The Russian army allied with Prussia was badly beaten at the battle of Friedland on 14 June, 1807. But while Napoleon dealt harshly with Prussia, he saw in the young Tsar of Russia, Alexander, a potential ally against the Continental powers.

The friendship that Napoleon and Alexander proclaimed on a raft at Tilsit in 1807 carried the seeds of its own destruction. Napoleon wanted Russia as a satellite to his Empire, not as an ally. His creation of the Grand Duchy of Warsaw was viewed with alarm by the Russian aristocracy as a prelude to an independent state of Poland. Alexander was urged to reestablish Poland with himself as king, and in April 1812 he issued an ultimatum: Napoleon must evacuate his troops from Prussia and the Grand Duchy.

Napoleon was faced with a difficult choice. He was reluctant to make war on Russia. Yet he considered the Grand Duchy essential to maintaining the existing frontiers of his Empire. He assembled more than half-a-million men, only half of which were French, at the Polish border, and on the night of 23/24 June, 1812, the advance guard crossed from the Grand Duchy of Warsaw over the River Niemen into Russia.