Siemowit IV (ca. 1353/1356 – 21 January 1426) was one of the Dukes of Masovia

Dukes of Masovia

The Dukes of Masovia were a line of the Piast dynasty who ruled in Masovia. The following is a list of all rulers of the Duchy of Masovia and its parts...

 of the old Polish Piast royal family. His domain included the lands of Czersk

Czersk

Czersk is a town in northern Poland in Chojnice County, Pomeranian Voivodeship.On July 1, 2006 this municipality celebrated 80 years of granting this community the status of city....

, Rawa

Rawa Mazowiecka

Rawa Mazowiecka is a town in central Poland, with 17,765 inhabitants . It lies in the Łódź Voivodeship and is the capital of Rawa County.First mentioned in 1288, it received city rights in 1321....

, Sochaczew

Sochaczew

Sochaczew is a town in central Poland, with 38,300 inhabitants . Situated in the Masovian Voivodeship , previously in Skierniewice Voivodeship . It is the capital of Sochaczew County....

, Płock and Gostynin

Gostynin

Gostynin is a town in Central Poland with 19,414 inhabitants . It is situated in the Masovian Voivodship since 1999 and was previously in the Płock Voivodship from 1975 to 1998. It is the capital of Gostynin County.-External links:*...

. In 1381 he inherited Wisz and in 1387 Bełz

Belz

Belz , a small city in the Lviv Oblast of Western Ukraine, near the border with Poland, is located between the Solokiya river and the Rzeczyca stream....

.

Life

Siemowit IV was a son of Siemowit III

Siemowit III of Masovia

Siemowit III of Masovia was a prince of Masovia and a co-regent of the lands of Warsaw, Czersk, Rawa, Gostynin and other parts of Masovia.- Life :...

. After the death of Louis I of Hungary 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

Szlachta

The szlachta was a legally privileged noble class with origins in the Kingdom of Poland. It gained considerable institutional privileges during the 1333-1370 reign of Casimir the Great. In 1413, following a series of tentative personal unions between the Grand Duchy of Lithuania and the Kingdom of...

 from Lesser Poland

Lesser Poland

Lesser Poland is one of the historical regions of Poland, with its capital in the city of Kraków. It forms the southeastern corner of the country, and should not be confused with the modern Lesser Poland Voivodeship, which covers only a small, southern part of Lesser Poland...

 and armies of Hungary

Hungary

Hungary , officially the Republic of Hungary , is a landlocked country in Central Europe. It is situated in the Carpathian Basin and is bordered by Slovakia to the north, Ukraine and Romania to the east, Serbia and Croatia to the south, Slovenia to the southwest and Austria to the west. The...

. In 1386 he accepted the rule of King of Poland Jadwiga of Poland

Jadwiga of Poland

Jadwiga was monarch of Poland from 1384 to her death. Her official title was 'king' rather than 'queen', reflecting that she was a sovereign in her own right and not merely a royal consort. She was a member of the Capetian House of Anjou, the daughter of King Louis I of Hungary and Elizabeth of...

 and her king-consort

Consort

Consort may refer to:Titles:* Queen consort, wife of a reigning king* Prince consort, husband of a reigning queen* King consort, rarely used alternative title for husband of a reigning queen...

 Grand Duke of Lithuania Władysław II Jagiełło and became a hereditary vassal

Vassal

A vassal or feudatory is a person who has entered into a mutual obligation to a lord or monarch in the context of the feudal system in medieval Europe. The obligations often included military support and mutual protection, in exchange for certain privileges, usually including the grant of land held...

 of Poland

Poland

Poland , officially the Republic of Poland , is a country in Central Europe bordered by Germany to the west; the Czech Republic and Slovakia to the south; Ukraine, Belarus and Lithuania to the east; and the Baltic Sea and Kaliningrad Oblast, a Russian exclave, to the north...

. The following year he married the sister of the Polish king-consort, Aleksandra

Alexandra of Lithuania

Alexandra was the youngest daughter of Grand Duke of Lithuania Algirdas and his second wife Uliana of Tver. In 1387 Alexandra married Siemowit IV, Duke of Masovia...

, and received the land of Bełz

Duchy of Belz

Duchy of Belz or principality of Belz was a petty duchy, formed in the late 12th century in Kievan Rus. During its history the duchy was a constituent part of some other political entities such as the Kingdom of Rus, the Kingdom of Hungary, Duchy of Masovia when eventually in the late 14th century...

.

He lost much of his domain to the Teutonic Order, including Wizna

Wizna

Wizna is a village in Łomża County of Podlaskie Voivodeship, in north-eastern Poland. The Biebrza River flows through town. Wizna is also known for the battle of Wizna which took place in its vicinity during the 1939 Invasion of Poland. At present, farming and food production are the primary...

, 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

Battle of Grunwald

The Battle of Grunwald or 1st Battle of Tannenberg was fought on 15 July 1410, during the Polish–Lithuanian–Teutonic War. The alliance of the Kingdom of Poland and the Grand Duchy of Lithuania, led respectively by King Jogaila and Grand Duke Vytautas , decisively defeated the Teutonic Knights, led...

 he fielded three banners of his own troops, fighting alongside the 'Royal' Poles.

He had 5 sons ( prince Siemowit V of Masovia, prince Kazimierz II of Belz, prince Trojden II, prince Władysław I of Plock,and future bishop Alexander Ziemowit) , and 7 daughters with Alexandra and their 6 daughters married European princes and feudal lords: Bogislaw IX (Maria or Mary of Masovia), Ernest the Iron( Cymburgis of Masovia

Cymburgis of Masovia

Cymburgis of Masovia in January 1412 became the second wife of the Habsburg Duke Ernest the Iron of Austria and thus a Duchess/Archduchess of the Inner Austrian line in Styria, Carinthia and Carniola.Cimburgis was born at Warsaw in the Duchy of Masovia to Duke...

), Bolesław I of Cieszyn (Euphemia or Ofka), Wilhelm II. der Reiche (Amelia of Masovia), Michael Žygimantaitis (Katarzyna or Catherine of Masovia ), János Garai (Jadwiga of Masovia ), while his grandson was Frederick III, Holy Roman Emperor

Frederick III, Holy Roman Emperor

Frederick the Peaceful KG was Duke of Austria as Frederick V from 1424, the successor of Albert II as German King as Frederick IV from 1440, and Holy Roman Emperor as Frederick III from 1452...

 and his granddaughter was Dorothy Garai

Dorothy Garai

Dorothy Garai was Queen consort of Bosnia as spouse of King Tvrtko II of Bosnia.-Family and engagement:She was the daughter of powerful Hungarian nobleman, John Garai, who governed Croatia as ban, and a descendant of a notable Hungarian noble family of Garai. Dorothea's grandfather was Palatine...

, Queen of Bosnia.