Former duchy in Poland
The Duchy of Warsaw was a feudal district duchy in Masovia, centered on the Warsaw Land. Its capital was Warsaw.
The state was established in 1310, in the partition of the Duchy of Masovia, with duke Siemowit II of Masovia becoming its first leader. It existed until 5 November 1370, when, under the rule of duke Siemowit III, duchies of Czersk, Rawa, and Warsaw were unified into the Duchy of Masovia. It was again re-established in June 1381, in the partition of the Duchy of Masovia, with duke Janusz I of Warsaw as its first leader. It existed until 1488, when it got incorporated into the Duchy of Czersk.
From 1310 to 1320, it was a fiefdom within the Kingdom of Poland, and from 1320 to 1385, a fiefdom of the United Kingdom of Poland, and from 1386 to 1488, a fiefdom of the Crown of the Kingdom of Poland.
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