Конрад Мазовецкий: Жизнь и правление польского князя

Konrad I of Masovia (ca. 1187/88 – 31 August 1247), from the Polish Piast dynasty, was the sixth Duke of Masovia and Kuyavia from 1194 until his death as well as High Duke of Poland from 1229 to 1232 and again from 1241 to 1243.

Konrad was the youngest son of High Duke Casimir II the Just of Poland and Helen of Znojmo, daughter of the Přemyslid duke Conrad II of Znojmo (ruler of the Znojmo Appanage in southern Moravia, part of Duchy of Bohemia). His maternal grandmother was Maria of Serbia, apparently a daughter of the pre Nemanjić župan Uroš I of Rascia. After his father's death in 1194, Konrad was brought up by his mother, who acted as regent of Masovia. In 1199, he received Masovia and in 1205 the adjacent lands of Kuyavia as well. In 1205, he and his brother, Duke Leszek I the White of Sandomierz, had their greatest military victory at Battle of Zawichost against Prince Roman the Great of Galicia–Volhynia. The Ruthenian army was crushed and Roman was killed in battle. The Rurik princess Agafia of Rus became his wife.

In an effort to enlarge his dominions, Konrad unsuccessfully attempted to conquer the adjacent pagan lands of Chełmno in Prussia during a 1209 crusade with the consent of Pope Innocent III. In 1215, the monk Christian of Oliva was appointed a missionary bishop among the Old Prussians, his residence at Chełmno however was devastated by Prussian forces the next year. Several further campaigns in 1219, 1222 failed, instead Konrad picked a long term border quarrel with the Prussian tribes. The duke's ongoing attempts on Prussia were answered by incursions across the borders of his Masovian lands, while Prussians were in the process of gaining back control over the disputed Chełmno Land and even threatened Konrad's residence at Płock Castle. Subjected to constant Prussian raids and counter raids, Konrad now wanted to stabilize the north of his Duchy of Masovia in this fight over the border area of Chełmno.

Konrad was also entangled in the conflict over the Polish Seniorate Province with his Piast cousin Duke Władysław III Spindleshanks of Greater Poland and assumed the title of a Polish High Duke in 1229. However their Silesian relative Duke Henry I the Bearded finally prevailed as High Duke at Kraków in 1232 and confined Konrad's rule again to Masovia. When Henry's son and heir, High Duke Henry II the Pious was killed at the 1241 Battle of Legnica, Konrad once again assumed the senioral title, but had to yield to the claims raised by his nephew Bolesław V the Chaste, son of his elder brother Leszek, two years later.

Around 1208/1209 Konrad married Agafia of Rus, daughter of Prince Svyatoslav III Igorevich. They had ten children:
Bolesław I (c. 1210 – 17 April 1248), Duke of Masovia
Casimir I (c. 1210/13 – 14 December 1267), Duke of Kuyavia
Siemowit I (c. 1215 – 24 June 1262), succeeded eldest brother as Duke of Masovia. Eudoxia (b. c. 1215–1225), married Count Dietrich I of Brehna and Wettin
Ludmila, probably a norbertine nun at Płock. Ziemomysł (c. 1220 – 10 July/18 September 1241). Salomea (c. 1220/1225 – aft. 30 August 1268? ), probably a clare nun at Skała. Judith (c. 1222/27 – 4 December 1257/63), married firstly to Duke Mieszko II the Fat of Opole, secondly to Duke Henry III the White of Wrocław. Dubrawka (b. c. 1230, d. 1265). Mieszko (bef. 1236 – bef. 1238), died in infancy

Konrad is considered by Poles to be responsible for Teutonic Knights' control of most of the Baltic coastline, undermining Polish authority in the area. King Casimir III of Poland had to accept the rule of the Order in Thorn and Kulm by the 1343 Treaty of Kalisz. After the Thirteen Years' War in the 1466 Second Peace of Thorn, the Polish King Casimir IV Jagiellon gained control over the Chełmno Land as part of Royal Prussia.