Mikołaj Sieniawski was a notable Polish

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...

 magnate

Magnate

Magnate, from the Late Latin magnas, a great man, itself from Latin magnus 'great', designates a noble or other man in a high social position, by birth, wealth or other qualities...

, military commander and a prominent politician of his times. He built Brzeżany Castle round which the modern town of Berezhany

Berezhany

Berezhany is a city located in the Ternopil Oblast of western Ukraine. It is the administrative center of the Berezhanskyi Raion , and rests about 100 km from Lviv and 50 km from the oblast capital, Ternopil. The city has a population of about 20,000, and is about 400 m above sea level...

 has developed.
He is not to be confused with his descendant Mikołaj Hieronim Sieniawski, who was also a hetman in 1682 and 1683.

Since 1539 Mikołaj Sieniawski served as a Field Hetman of the Crown

Hetman

Hetman was the title of the second-highest military commander in 15th- to 18th-century Poland and the Grand Duchy of Lithuania, which together, from 1569 to 1795, comprised the Polish-Lithuanian Commonwealth, or Rzeczpospolita....

 and took part in most wars Poland was engaged in. Most notably he organized several successful raids to the area of the Ottoman Empire

Ottoman Empire

The Ottoman EmpireIt was usually referred to as the "Ottoman Empire", the "Turkish Empire", the "Ottoman Caliphate" or more commonly "Turkey" by its contemporaries...

 and Crimea

Crimea

Crimea , or the Autonomous Republic of Crimea , is a sub-national unit, an autonomous republic, of Ukraine. It is located on the northern coast of the Black Sea, occupying a peninsula of the same name...

. Between 1542 and 1553 he was also the voivode of Belz

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....

, and after that time he rose to be a voivod of the Ruthenian Voivodship, one of the richest and most populous regions of the Republic

Rzeczpospolita

Rzeczpospolita is a traditional name of the Polish State, usually referred to as Rzeczpospolita Polska . It comes from the words: "rzecz" and "pospolita" , literally, a "common thing". It comes from latin word "respublica", meaning simply "republic"...

. In 1563 he was promoted to the rank of Grand Crown Hetman, that is the de facto commander in chief of the Polish army.