Administrative division of the Duchy of Warsaw was based on departments, which were headed by prefects. It was a solution adopted after the French model, as the entire Duchy was in fact created by Napoleon, and based on French ideas, although the departaments were divided into traditional Polish powiats (counties). There were six initial departments, which had previously made Kingdom of Prussia’s province of South Prussia (1793/95 - 1807), but after the 1809 Polish–Austrian War, and the Treaty of Schönbrunn, their number increased to ten (as the Duchy territory was expanded following the annexation of West Galicia). Each department was named after its capital city.
The departments were divided into powiats, and the powiats were divided into urban and rural gminas. Each department was governed by a prefect, while counties were administered by a prefect deputy (Polish: podprefekt). Main cities of the Duchy (Warsaw, Poznan, Kalisz, Torun, Lublin, Kraków and Sandomierz) were administered by mayors (Polish: prezydent), who were nominated by King Frederick Augustus I. The initial six departaments were created by a Napoleon’s decree of January 14, 1807.
In January 1807 the Duchy of Warsaw was divided into the following departaments:
Added in 1809, after the Polish - Austrian War (the four departaments of former West Galicia were created by a royal decree on February 24, 1810. On April 17, 1810, they were divided into forty counties):
In 1815 the Duchy of Warsaw was divided into Prussian-administered Grand Duchy of Poznań and Russian-controlled Congress Poland. In 1816, the departments of Congress Poland were turned into voivodeships (see Administrative division of Congress Poland).