Siemowit IV, Duke of Masovia

Siemowit IV, also known as Siemowit IV the Younger, was born around the year thirteen fifty-three to thirteen fifty-six. He was a prominent Polish prince and a member of the Masovian branch of the illustrious House of Piast. His reign began in the years of thirteen seventy-three or thirteen seventy-four when he became the Duke of Rawa. Following the division of his father's inheritance in thirteen eighty-one, he ruled over several significant territories including Rawa, Płock, Sochaczew, Gostynin, Płońsk, and Wizna.

As the second son of Siemowit III, Duke of Masovia, and Euphemia, the daughter of Nicholas II of Opava, Siemowit IV was well-positioned within the aristocracy. His governance was marked by territorial challenges; during the years of thirteen eighty-two to fourteen hundred one, he lost control of Wizna, and between thirteen eighty-four and fourteen hundred, he faced the loss of Zawkrze and Płońsk to the Teutonic Order.

Despite these setbacks, Siemowit IV's influence remained significant. After becoming a hereditary Polish vassal in thirteen eighty-six, he expanded his rule to include Belz by thirteen eighty-eight. His leadership was characterized by the complexities of feudal allegiances and the ongoing conflicts of the era, which shaped the political landscape of Masovia.

Siemowit IV's legacy is intertwined with the history of the region, reflecting the turbulent times of the late fourteenth and early fifteenth centuries. He passed away on the twenty-first of January in fourteen twenty-six, leaving behind a rich history as a ruler who navigated the challenges of his time.