Bolesà Âaw II of Masovia or Bolesà Âaw II of Pà Âock (pl: Bolesà Âaw II mazowiecki (pà Âocki); ca. 1253/58 – 20 April 1313), was a Polish prince, member of the House of Piast, Duke of Masovia during 1262-1275 jointly with his brother, after 1275 sole ruler over Pà Âock, after 1294 ruler over all Masovia and Duke of Kraków and Sandomierz during 1288-1289. In 1310 he gave to his sons the districts of Warsaw and Czersk. Also High duke of Poland twice (1288, 1289).
He was younger son of Siemowit I of Masovia and Pereyaslava, a Rus' princess, who was according to some historians a daughter of Prince Daniel of Halych or according to others his distant relative. He was born around 1253-1258.
Nothing is known from Bolesà Âaw II's first years, except that in 1262 he wasn't with his father and older brother Konrad II during the siege and battle of Jazdów, where Siemowit I was killed and Konrad II was captured by the Lithuanians. Because Bolesà Âaw II was too young to rule by himself, the regency was exercised by his mother Pereyaslava and his late father's ally, Bolesà Âaw the Pious, Duke of Greater Poland, until 1264, when his brother Konrad II was liberated and returned to assume the government.
When Bolesà Âaw II attained his majority in 1275, he demanded from his brother his part over their paternal inheritance. As a result, he received the western part of Masovia, with his capital in Pà Âock. However he was not satisfied with this distribution, evidenced in his long-standing conflict with Konrad II; during this fight, Bolesà Âaw II did not hesitate to ask for the help from the murderers of his father, the Lithuanians. The alliance between Bolesà Âaw II and Lithuania was strengthened in 1279 when he married GaudemantÃÂ, the daughter of Grand Duke Traidenis, who in her baptism took the name of Sophia.
Another ally of Bolesà Âaw II was his cousin Wà Âadysà Âaw I the Elbow-high, who was then Duke of Kujawy. The war between Bolesà Âaw II and Konrad during the second half of the 1270s and the first half of the 1280s didn't benefit any party, only causing destruction in extended parts of Masovia.
On 30 September 1288 Leszek II the Black died childless. Part of the local nobility, led by Paweà  of Przemankowo, Bishop of Kraków and the Topór family supported the succession of Bolesà Âaw II.
However, he wasn't the only candidate for the Seniorate. Henryk IV Probus, Duke of Wrocà Âaw, also advanced his claims. At first, it seemed that Bolesà Âaw II was able to master Lesser Poland without obstacles, as his troops in 1288 captured Kraków and Sandomierz. However, later in the same year he was expelled from Kraków by the troops of Henryk IV Probus, who gained the decisive favor of the castellan Sulk the Bear (pl: Suà Âk z Niedà ºwiedzia), who opened the gates of Wawel Castle to him. After this victory, Henryk IV Probus returned to Wrocà Âaw, and Bolesà Âaw II managed to say in Sandomierz. In early February 1289 a coalition of Piast princes (Henry III of Gà Âogów, Przemko of à Âcinawa and Bolko I of Opole) organized an expedition to Kraków with the purpose of consolidating the rule of Henryk IV Probus. At the sime time Bolesà Âaw II, who still wanted to recover Kraków, organized a coalition with Wà Âadysà Âaw I the Elbow-high and Casimir II of à ÂÃÂczyca, Unexpectedly, he also received the support of his brother Konrad II and Kievan Rus' troops. In this way, Bolesà Âaw II was able to organized a powerful army with the main objective of reconquering the Seniorate. The army of Henryk IV Probus withdrew from Kraków, and on 26 February the bloody Battle of Siewierz took place, which ended with the defeat of Henryk IV's allies; during the fight, was killed Przemko of à Âcinawa and Bolko I of Opole was captured. After the battle, Bolesà Âaw II occupied Kraków, where he triumphantly entered in the summer of 1289. Shortly after, he gave Sandomierz to his brother Konrad II as they had previously accorded in exchange of his military support. This action caused outrage among the Lesser Poland nobility (accustomed to see the Duke of Kraków reign over Sandomierz), who utterly refused to recognize Bolesà Âaw II as their ruler, and proclaimed Wà Âadysà Âaw I the Elbow-high as the new Duke of Kraków. For unknown reasons, Bolesà Âaw II refused to fight and retreated to his domains in Pà Âock, and in August 1289 Wà Âadysà Âaw I the Elbow-high was in turn expelled by Henryk IV Probus, who became in the new ruler over Kraków and Sandomierz.
The only positive aspect of this struggle for the throne of Kraków was the reconciliation with his brother Konrad II.
Bolesà Âaw II's wife Sophia died in 1288. His second marriage was, like the first one, contracted for political reasons. The chosen bride was Princess Kunigunde, sister of King Wenceslaus II of Bohemia; the wedding took place in the first half of 1291. Thanks to this union, the Bohemian King neutralized the claims of the Duke of Pà Âock over the Seniorate, especially when he was able to conquer Kraków in 1291. Bolesà Âaw II also wanted to strengthen his position with Wenceslaus II, so he didn't hesitate when in 1292 he helped his brother-in-law in his war against Wà Âadysà Âaw I the Elbow-high.
The alliance between Masovia and Bohemia did not last very long. In 1294 Konrad II died without male offspring, so Bolesà Âaw II became the sole ruler over all Masovia. Feeling stronger, he broke relations with the Kingdom of Bohemia and reestablished relations with Wà Âadysà Âaw I the Elbow-high.
In 1295 Przemysà  II became King of Poland. The following year, after his assassination, Bolesà Âaw II supported Wà Âadysà Âaw I in his brief war against Henry III of Gà Âogów for the succession in Greater Poland.
The hostile policy towards the Kingdom of Bohemia forced Wenceslaus II to launch an attack against Masovia. Despite the siege and destruction of Pà Âock, Bolesà Âaw II didn't change his political course, evidenced by his refusal to recognize Wenceslaus II as King of Poland in 1300 and the repudiation of his wife Kunigunde, who was sent back to Prague in 1302.
In the early 1300s Bolesà Âaw II founded the stronghold of Warsaw, contributing to its development in detriment of the nearby Czersk.
After 1305 Bolesà Âaw II was not present in any more political activity. The next information about him took place in 1310, when he granted two separate districts to his eldest two sons: Siemowit II received Warsaw and Trojden I received Czersk. In 1311, Borzysà Âaw becomes his Chancellor.
Bolesà Âaw II died on 20 April 1313 in Wyszogród and was buried at Pà Âock Cathedral.
In 1279 Bolesà Âaw II married firstly to Gaudemantà(baptized as Sophia; d. 1288), a daughter of Grand Duke Traidenis of Lithuania. They had three children:
In 1291 Bolesà Âaw II married secondly to Kunigunde (January 1265 - 27 November 1321), a daughter of Ottokar II and sister of Wenceslaus II, Kings of Bohemia; in 1302 Boleslaw and Kunigunde were divorced and she was sent back to Prague, where she became a nun. They had two children: