The duchy was held in personal union by Napoleon's ally, Frederick Augustus I of Saxony, who became the duke of Warsaw and remained a legitimate candidate for the Polish throne.

The newly recreated state was formally an independent duchy, allied to France, and in a personal union with the Kingdom of Saxony.

King Frederick Augustus I of Saxony was compelled by Napoleon to make his new realm a constitutional monarchy, with a parliament (the Sejm of the Duchy of Warsaw).

[10] After the Battle of Wagram, the ensuing Treaty of Schönbrunn allowed for a significant expansion of the duchy's territory southwards with the regaining of once-Polish and Lithuanian lands.

On 28 June, the Sejm formed the General Confederation of the Kingdom of Poland, establishing a system of government similar to the former commonwealth with the hope of reclaiming the partitioned territories.

However, Napoleon did not want to make a permanent decision that would tie his hands before his anticipated peace settlement with Russia, and did not recognize the confederation of 28 June.

Napoleon's Grande Armée, including a substantial contingent of Polish troops, set out with the purpose of bringing the Russian Empire to its knees, but his military ambitions were frustrated by his failure to supply the army in Russia and Russia's refusal to surrender after the capture of Moscow; few returned from the march back.

After Napoleon's defeat in the east, most of the territory of the Duchy of Warsaw was occupied by Russia in January 1813 during their advance on France and its allies.

Alexander I of Russia created a Provisional Highest Council of the Duchy of Warsaw to govern the area through his generals.

The Kulmerland and Gdańsk (Danzig) became part of the Province of West Prussia; the remaining territories (i.e., Greater Poland/Poznań), which covered an area of approximately 29,000 km2 (11,000 sq mi), were reconstituted into the Grand Duchy of Posen.

Finally, the bulk of the former Duchy of Warsaw, measuring some 128,000 km2 (49,000 sq mi), was re-established as what is commonly referred to as the "Congress Kingdom" of Poland, in a personal union with the Russian Empire.

Added in 1809: The duchy's armed forces were completely under French control via its war minister, Prince Józef Poniatowski, who was also a Marshal of France.

In fact, the duchy was heavily militarized, bordered as it was by Prussia, the Austrian Empire, and Russia, and it was to be a significant source for troops in various campaigns of Napoleon.

The heavy drain on its resources by forced military recruitment, combined with a drop in exports of grain, caused significant problems for the duchy's economy.

To make matters worse, in 1808 the French Empire imposed on the duchy an agreement at Bayonne to buy from France the debts owed to it by Prussia.

[14] Superficially, the Duchy of Warsaw was just one of the various states set up during Napoleon's dominance over Eastern and Central Europe, lasting only a few years and passing with his fall.

However, its establishment a little over a decade after the Second and Third Partitions, that had appeared to wipe Poland off the map, meant that Poles had their hopes rekindled of a resurrected Polish state.