The two treaties of Tilsit (7 and 9 July 1807) ended the War of the Fourth Coalition and saw Napoleon impose very different terms on the Russians and Prussians.
The war began in the summer of 1806 when Prussia had finally decided to make a stand against Napoleon, a year after their involvement in the Third Coalition might have prevented the crushing defeat of Austria. Napoleon moved quickly, and the Prussians suffered heavy defeats at Jena and Auerstadt (14 October 1806). Over the next few weeks the remaining Prussian troops were pursued by the French, and the King and Queen of Prussia were forced to take refuge in the far eastern part of their kingdom, near to their Russian allies.
Napoleon was not immediately successful against the Russians. His winter campaign of 1806-1807 ended with the costly drawn battle of Eylau (8 Februay 1807), fought in heavy snow in East Prussia. Both sides went into winter quarters. Napoleon spent the time rebuilding his armies and besieging Danzig. By mid-May the fall of Danzig was inevitable, and Napoleon began to plan for a fresh offensive. To his surprise the Russians moved first, on 5 June, but their offensive was ill handled and was abandoned on 7 June. Napoleon pursued the Russians, and despite a setback at Heilsberg on 10 June finally got his decisive victory at Friedland on 14 June 1807. The Russians lost about a third of their army, and Tsar Alexander was finally ready to discuss peace. As the French approached the Niemen, Russian envoys reached Napoleon's camp offering an armistice. A four-week long armistice came into effect on 23 June, and the two Emperors met for the first time on a raft in the middle of the Niemen River on 25 June.
This was the start of two weeks of negotiations that produced two treaties, one with Russia and one with Prussia. The treaty with Russia had public and secret terms, and established an alliance between the two powers. In contrast the treaty with Prussia was public and humiliating.
The main public terms of the treaty with Russia included an agreement that Danzig should become a free city under the joint protection of the Kings of Prussia and Saxony. In reality it was ruled by the French. Prussia lost her Polish provinces and they were used to form a new Duchy of Warsaw, to be ruled by the King of Saxony. Napoleon agreed to accept Russian mediation between France and Britain. In return Alexander agreed to recognise Napoleon's brother's Joseph and Louis and kings of Naples and Holland, and Jerome as King of the newly formed Kingdom of Westphalia. He also officially recognised the Confederation of the Rhine and the titles of all of its members. Westphalia was to be made of a mix of former Prussian provinces west of the Elbe and other German states already ruled by Napoleon. The Russians accepted French mediation in their war with the Ottoman Turks, and agreed to retreat from Wallachia and Moldavia once that peace had been ratified.
The secret articles saw the two Emperors agree to an alliance. Both agreed to support the other in any war against other European powers. Other terms built on the terms of the public treaty. Alexander agreed to withdraw his ambassador from Britain if the British government didn't agree to Russian mediation. He also agreed to use his influence to convince Denmark, Sweden and Portugal to do the same, to close their ports to British ships and to declare war if the mediation was refused. In return the French agreed to support the Russians against the Ottoman Empire, and in particular to help them seize all of the Empire's European provinces apart from Constantinople and Roumalia.
The treaty with Prussia was much harsher. Prussia was reduced to its borders of 1772, losing its Polish lands and all lands west of the Elbe. The French also kept the fortress of Magdeburg. Frederick William III, King of Prussia had to recognise the Napoleonic kingdoms of Westphalia, Naples and Holland and the Confederation of the Rhine. The Kingdom of Westphalia was largely created out of former Prussian lands. All Prussian treaties with states west of the Elbe were declared null and void. A secret clause also committed Prussia to joining the war against Britain.
The treaty with Russia was signed on 7 July 1807. The treaty with Prussia followed two days later, on 9 July 1807. A second treaty with Prussia, signed on 12 July, forced the Prussians to accept French occupation until a war indemnity had been paid, and in 1808 this was set at 140 million francs.
The treaties of Tilsit appeared to place Napoleon at the peak of his powers, dominating Europe from France to the Russian border and into Italy, and in many ways it was indeed a triumph. However the harsh terms of the treaty with Prussia ensured that the Prussians would never accept the new settlement, while the relationship with Russian soon began to come under strain. Napoleon was disappointed with the level of Russian aid during his war with Austria in 1809, while the Continental System caused great problems within Russia. Only five years later the French invaded Russia, at the start of the most disastrous campaign of Napoleon's career.