Napoleon's Grande Armée crosses the Neman

Preparations for the Crossing. In March 1811 Davout received orders to clandestinely prepare a demonstration of military strength aimed at impressing Russia. Extensive magazines were set up in towns across Poland and East Prussia, and the Vistula river valley was developed into a vital supply base in 1811–1812. France and Austria signed an alliance treaty on 14 March 1812. After two days of preparation, the invasion commenced on Wednesday, 24 June [O.S. 12 June] 1812.

The Crossing of the Neman. Beginning on 24 June 1812, the initial wave of the multinational Grande Armée crossed the Neman River, marking the entry from the Duchy of Warsaw into Russia. Around 400,000–500,000 men, described as the largest army assembled up to that point in European history, crossed the border and headed towards Moscow. The crossing at the outset of the invasion was later described in Tolstoy's War and Peace and mentioned in Pan Tadeusz.