1807
Napoleon's attempts to build and expand his empire kept Europe at war for almost a decade and brought him into conflict with the same European powers that had beleaguered Poland in the last decades of the previous century. An alliance of convenience was the result of this situation. Volunteer Polish legions attached themselves to Bonaparte's armies, hoping that in return the emperor would allow an independent Poland to reappear out of his conquests.
The Duchy of Warsaw was a Polish state established by Napoleon in 1807 from the Polish lands ceded by the Kingdom of Prussia under the terms of the Treaties of Tilsit. The duchy was held in personal union by one of Napoleon's allies, King Frederick Augustus I of Saxony.
Read more about this topic: Territorial Evolution Of Poland