Siemowit IV, duke of Masovia

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prince Siemowit of Masovia (House of Piast), IV

Polish: kn. Siemowit Mazowiecki, IV, German: Ziemowit von Masowien, IV
Also Known As: "Ziemowit / Siemowit IV the Younger"
Birthplace: Czersk, Mazowieckie, Poland
Death: December 05, 1425
Czersk, Mazowieckie, Poland
Place of Burial: Plock, Płock County, Masovian Voivodeship, Poland
Immediate Family:

Son of Książę Siemowit III "Starszy" Prince of Mazovia and Euphemia von Troppau
Husband of Alexandra of Lithuania
Ex-partner of ?
Father of Mikłusz; Duke Siemowit V of Masovia; Hedvig Garay; Cymburgis of Masovia; Aleksander mazowiecki and 10 others
Brother of Anna; Eufemija Siemovitaitė; Janusz I Starszy ks. Piast-Mazowiecki, książę and Margaret of Masovia
Half brother of NN; NN and Henrik of Mazovia

Occupation: duke of Masovia, prince of Polotsk and Kuyavia
Managed by: Private User
Last Updated:

About Siemowit IV, duke of Masovia

ZIEMOWIT, Prince of Plock and Kujavia

  • He was the second son of Siemowit III, Duke of Masovia and his first wife Euphemia, daughter of Nicholas II of Opava.
  • ZIEMOWIT (before 1352-5 Dec 1425). He succeeded as Prince of Plock and Kujavia. m ([1387]) ALEKSANDRA of Lithuania, daughter of ALGIRDAS [Olgierd] Grand Duke of Lithuania & his second wife Iuliana Aleksandrovna of Tver [Rurikid] (-19 Jun 1434).
  • Buried in the Ducal crypt at Płock Cathedral.


  • Married in 1387 ALEKSANDRA of Lithuania, daughter of ALGIRDAS [Olgierd] Grand Duke of Lithuania & his second wife Iuliana Aleksandrovna of Tver [Rurikid] (-19 Jun 1434).

Prince Ziemowit & his wife ALEKSANDRA, had twelve children:

  • 1) ZIEMOWIT [1389]-17 Feb 1442). He succeeded as Prince of Gostyn. m ([1435/37]) as her second husband, MARGARETA von Ratibor, widow of KASIMIR Herzog von Auschwitz, daughter of JOHANN II Herzog von Troppau, Ratibor und Jägerndorf [P%C5%99emyslid] & his wife Helena of Lithuania ([1410]-5 Jul 1459). Prince Ziemowit & his wife had one child: A) MARGARETA ([1436/41]-1483 after 5 May). m ([1447/53]) KONRAD IX Herzog von Oels, son of KONRAD V Herzog von Oels und Wohlau [Piast] & his wife Margareta --- ([1415/20]-14 Aug 1471).
  • 2) JADWIGA shortly before 16 Nov 1393-after 19 Feb 1439). m (after 3 Jan 1410) JANOS Garay, son of MIKLÓS [I] Garay & his wife --- (-before 9 Apr 1428).
  • 3) CIMBURKA Warszawa [1394/97]-Türnitz 28 Sep 1429, bur Lilienfeld Stiftskirche). The Necrologium Austriacum refers to the wife of Duke Ernst as "des hertzog von der Nasaw tochter…fraw Cinburga von Polen", records her death in 1426 and her burial at Lilienfeld[542]. The necrology of Rein records the death "III Kal Oct" of "Cimburga ducissa Austrie et Stirie"[543]. m (Krakow 25 Jan 1412) as his second wife, ERNST I "der Eiserne" Duke of Austria, son of LEOPOLD III Duke of Austria & his wife Verde Visconti (Bruck an der Mur 1377-Bruck an der Mur 10 Jun 1424, bur Rein, Steiermark).
  • 4) EUPHEMIA [1395/98]-[25 Jul/17 Sep] 1447). m (dispensation 27 Jan 1412) as his second wife, BOLKO I Herzog von Teschen und Auschwitz, son of PREMISLAW I Herzog von Teschen & his wife Elisabeth von Beuthen [Piast] (-6 May 1431).
  • 5) ALEKSANDER [1400-2 Jun 1444). Provost at Gnesen Cathedral 1414/29. Rektor of Krakow 1422. Bishop of Triento 1423. Patriarch of Aquileia 1436. Cardinal 1440. Provost of St Stephan in Vienna [1443].
  • 6). AMELIA [1396/99]-after 17 May 1424). m (16 May 1413) WILHELM II "der Reiche" joint Markgraf von Meissen, son of FRIEDRICH III "der Strenge" joint Markgraf von Meissen & his wife Katharina von Henneberg (23 Apr 1371-30 Mar 1425, bur Meissen Cathedral).
  • 7) KAZIMIERZ (1396/1407]-15 Sep 1442). He succeeded as Prince of Plock and Kujavia. m (26 Jun 1442) MARGARETA Szamotuły, daughter of WINCENZ Szamatuły Castellan of Meseritz (-5 Nov 1464). She married secondly (before 12 Jan 1445) Wenzel II Herzog von Troppau und Ratibor (-29 Oct 1456).
  • 8) TROJDEN (1397/1410]-24 Jul 1427). He succeeded as Prince of Plock.
  • 9) WŁADYSŁAW [1398/1411]-11/12 Dec 1455). He succeeded as Prince of Plock. m ([1444]) ANNA von Oels, daughter of KONRAD Herzog von Oels und Wohlau [Piast] & his wife Margareta --- ([1420/30]-1481 before 29 Mar). Prince Władysław & his wife had two children: 1) ZIEMOWIT (2 Jan 1446-1 Jan 1462). He succeeded in 1459 as Prince of Plock. #2) WŁADYSŁAW (after 31 Oct 1448-27 Feb 1462). He succeeded as Prince of Plock and Gostyn.
  • 10) ANNA ([13 Jun 1407/1413]-before 7 Feb 1435). m (before 26 May 1427) as his first wife, MICHAEL BOLESŁAW of Lithuania, son of KORYBUT ŽYGIMANTES [Siegmund] of Lithuania Prince of Trock, Motchaisk and Starodub [later Grand Duke of Lithuania] & his first wife --- Andreievna Pss Odynczewicza (before 1406-shortly before 10 Feb 1452).
  • 11) MARIA. [1408/19]-18 Feb [1454]). m ( Posen 24 Jun 1432) BOGISLAW IX Duke of Pomerania in Hinterpommern, son of BOGISLAW VIII Duke of Pomerania in Hinterpommern & his wife Sophie von Holstein (1407-7 Dec 1446)
  • 12) KATARZYNA after 29 Mar 1475). m ([1440/45]) as his third wife, MICHAEL BOLESŁAW of Lithuania, son of KORYBUT ŽYGIMANTES [Siegmund] of Lithuania Prince of Trock, Motchaisk and Starodub [later Grand Duke of Lithuania] & his first wife --- Andreievna Pss Odynczewicza (before 1406-shortly before 10 Feb 1452).

Source -

Grandchildren of Alexandra and Siemowit IV included

  • Frederick III, Holy Roman Emperor, Przemyslaus II, Duke of Cieszyn,
  • Sophie of Pomerania, Duchess of Pomerania
  • Dorothy Garai, queen of Bosnia.


This time the fight took place successfully for Siemowit IV: by the end of 1384 he could conquer Łęczyca. However, he soon realized that, given the power of the Polish-Lithuanian union (confirmed in the Union of Krewo), his forces are too small. Finally, he decided to make peace negotiations with Jadwiga, which ended successfully on 12 December 1385 with the signing of a treaty, under which Siemowit IV returned all the lands taken by him in exchange for the sum of 10,000 silver marks, and most important, he relinquished all his claims to the Polish crown and paid homage to the Queen Jadwiga and her new husband and King, Jogaila, from which he received the Duchy of Belz as dowry of Princess Alexandra of Lithuania, Jogaila's sister, who married Siemowit IV as a gesture of reconciliation between both parties.[3][4][5][6][7]

Siemowit IV's final testimony of complete resignation over the Polish crown was his attendance to the ceremonies of baptism, marriage and coronation of Jadwiga and Jogaila in Kraków. After these ceremonies, he renewed his homage to the royal couple. After this, he joined the royal entourage to Vilnius, where he participated in the process of Christianization of Lithuania.

After finally admitted his defeat and paid homage to the Polish King, the political situation of Siemowit IV was significantly deteriorated. Before the war, as an independent ruler he can effectively maneuver between the Polish, Lithuanians and the Teutonic Order; now, as a vassal was clearly seen as an ally of the Polish Kingdom. In addition, in order to finance his policies he needed money and several times he mortgaged some of his domains to the Teutonic Order, including Wizna (during 1382-1401), Płońsk (during 1384-1399) and Zawkrze (during 1384-1399 and 1407-1411).

In view of the growing friction between the Polish and Teutonic Order, Siemowit IV tried to obtain the greatest benefit for him and intervened as a mediator. Also, after the outbreak of the war of 1409–1410 between Poland, Lithuania and the Teutonic Order, the attitude of the Masovian Duke wasn't clear: in one side, he tried to contact King Sigismund of Hungary and by other side, he pressured his warring neighbors to maintain the peace. In view of the failure of his attempts to make a compromise, Siemowit IV finally sent his troops at the Battle of Grunwald, but his participation was only symbolic; in fact, was his son Siemovit V who fielded two banners of his own troops and fought alongside the 'Royal' Poles and Lithuanian troops.[8] In order to maintain his friendly relations with the Teutonic Order, he provides them with refunds even during the campaign; in exchange, the Order returned Zawkrze to Siemowit IV, despite the fact that under the Peace of Thorn (1411) they aren't obliged to do it.

Despite his official subordination to Poland, Siemowit IV tried to pursue an independent foreign policy. This was expressed in his frequent contacts with the Hungarian King Sigismund, who, wishing to drag a Polish vassal to his side gave the Masovian Duke the rich prebends from the Bishopric of Veszprém and other possessions across Hungary.

Siemowit IV's relations with Poland, although some temporary frictions caused by his too independent policy (he even minted his own coins) remained friendly, despite the fact that he didn't fulfill his duties as a vassal, and only sent troops to Poland occasionally when he was required to do. Another gesture of friendship with King Władysław II was noted when he used Siemowit IV's daughters into political marriages and the support given to his son Alexander in his Church career.

In domestic politics, Siemowit IV continued the economic restructuring which begun under the rule of his father. For this purpose, in addition to the existing statutes he implemented the Kulm law in several of his cities and promoted the colonization of the Masovian nobility to Belz.

After 1420 Siemowit IV, due to his progressive blindness, gradually gave participation in the government to his adult sons. In 1425, the dispute about the election of his Chancellor Stanisław z Pawłowic as Bishop of Płock didn't brought anything good to Masovia, and only forced his sons Siemowit V and Casimir II into a humiliating surrender.

Siemowit IV died on 21 January 1426 at Gostynin and was buried in the Ducal crypt at Płock Cathedral.

==Division of Masovia (1381–1426)==

Siemowit IV (also known as Ziemowit IV) (b. ca. 1353/1356[1], d. January 21, 1426[2]) was one of the Dukes of Masovia. His domain included the lands of Czersk, Rawa, Sochaczew, Płock and Gostynin. In 1381 he inherited Wisz and in 1387 Bełz. Siemowit IV was a son of Siemowit III. After the death of Ludwik Węgierski he was one of the pretenders to the Polish throne. In 1383 he conquered Cuyavia, but was soon expelled by the joint forces of szlachta from Lesser Poland and armies of Hungary. In 1386 he accepted the rule of Grand Duke of Lithuania and King of Poland Jogaila and became a hereditary vassal of Poland. The following year he married the sister of the Polish king, Aleksandra, and received the land of Bełz.

He lost much of his domain to the Teutonic Order, including Wizna, Zawkrze and Płońsk. To get it back, he took part in the war of 1409–1410 between Poland, Lithuania and the Teutonic Order. During the Battle of Grunwald he fielded three banners of his own troops, fighting alongside the Poles.


  • Siemowit IV (Ziemowit) – od 1373/1374 w Rawie, od 1381 r. w wyniku podziału, książę na Rawie, Płocku, Sochaczewie, Gostyninie, Płońsku i Wiźnie, od 1386 r. dziedziczny lennik Polski, od 1388 r. w Bełzie, strata ziemi wiskiej w latach 1382-1401, strata Zawkrza w latach 1384-1399 i 1407-1411, strata Płońska w latach 1384-1399 na rzecz zakonu krzyżackiego.
  • Kazimierz Jasiński: Rodowód Piastów mazowieckich. Poznań - Wrocław 1998, p. 87-88.
  • Kazimierz Jasiński: Rodowód Piastów mazowieckich. Poznań - Wrocław 1998, p. 88-89.
  • Supruniuk Anna, Setting the Duke of Mazovia Siemowit IV (1374-1426). Study of the political elite of Mazovia the late fourteenth and fifteenth century, Warsaw 1998
  • Supruniuk Anna, Siemowit V, in: Polish Biographical Dictionary, T.37.
  • Samsonowicz Henry, Supruniuk Anna,The political history (half of the XIV - the beginning of the sixteenth century),
  • Mazovia Siemowitów, in: History of Mazovia, v. 1 Pultusk 2006.
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Siemowit IV, duke of Masovia's Timeline

Czersk, Mazowieckie, Poland
Sochaczew, sochaczewski, mazowieckie, Poland
Sochaczew, Warszawa, Polen