In 1327, he became a vassal of the Bohemian crown; but, for unknown reasons, he didn't paid homage to King John of Luxembourg with the other Silesian Dukes in Opawa.
On 18 February 1327, together with the other Silesian Dukes, Bolesław paid homage to King John of Bohemia in Opawa.
#Katharina (b. ca. 1390 – d. 23 April 1422), married by 1410 to Duke Przemko I of Troppau (Opawa)
In 1336, Jan was forced to accept the annexation of the Duchy of Racibórz to the Přemyslid Duchy of Opawa.
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On 24 February 1327, together with the other Piast Dukes, Jan paid homage to King John of Bohemia in Opawa.
# Hedwig (b. ca. 25 March 1338 – d. ca. 1351), married by 11 August 1345 to Duke Nikolaus II of Opawa (Troppau).
On 19 February 1327, together with other Silesian rulers, Leszek paid homage to King John of Bohemia in Opawa.
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After his death, as a result of the arbitrary decision of King John of Bohemia (and despite the strong resistance of the other Piast rulers in Upper Silesia who were their closest male relatives), the Duchy of Racibórz was given to Duke Nicholas II of Opawa, who claimed the rights of his wife Anna, Leszek's oldest sister.
The settlement between King George and Nicholas I was signed on 16 August 1460: the King finally accepted the rule of the Duke of Opole over Strzelce, Niemodlin and Olesno, but in exchange Nicholas I had to resign his claims over the Duchy of Opawa (he bought the Duchy in 1454 from his co-ruler Ernest, but as a result of the King's strong opposition, Nicholas I wasn't able to take effective control over this land).
The next information about Siemowit is found on 19 February 1327, when, together with his brothers Władysław and George, he paid homage to the Bohemian King John of Luxembourg in Opawa.
Stefan Błachowski (Opawa, 19 May 1889 – 31 January 1962, Warsaw, Poland) was a Polish psychologist and professor at Poznań University.
The circumstances around the removal of Siemowit are unknown, and the next notices about him are found only on 19 February 1327, where Władysław, Siemowit and George paid homage to the Bohemian King John of Luxembourg in Opawa.
What is more, shortly after receiving news of the Ottokar II's defeat and death, the Duke of Opole-Racibórz attacked Opawa, probably wishing to obtain it.
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At first, the Duke of Opole-Racibórz supported the Hungarians, supporting Bolesław V the Chaste in his attacks over Opawa and Głubczyce.
Upon his arrival, he built a house at 290 Riverlaw Terrace in Opawa (these days a suburb of Christchurch).