BOLESLAUS II., called "The Bold," king of Poland (1039-1081), eldest son of Casimir I., succeeded his father in 1058. The domestic order and tranquillity of the kingdom had been restored by his painstaking father, but Poland had shrunk territorially since the age of his grandfather Boleslaus I., and it was the aim of Boleslaus II. to restore her dignity and importance. The nearest enemy was Bohemia, to whom Poland had lately been compelled to pay tribute for her oldest possession, Silesia. But Boleslaus's first Bohemian war proved unsuccessful, and was terminated by the marriage of his sister Swatawa with the Czech king Wratyslaus II. On the other hand Boleslaus's ally, the fugitive Magyar prince Bela, succeeded with Polish assistance in winning the crown of Hungary. In the East Boleslaus was more successful. In 1069 he succeeded in placing Izaslaus on the throne of Kiev, thereby confirming Poland's overlordship over Russia and enabling Boleslaus to chastise his other enemies, Bohemia among them, with the co-operation of his Russian auxiliaries. But Wratyslaus of Bohemia speedily appealed to the emperor for help, and a war between Poland and the Empire was only prevented by the sudden rupture of Henry IV. with the Holy See and the momentous events which led to the humiliating surrender of the emperor at Canossa. There is nothing to show that Boleslaus took any part in this struggle, though at this time he was on the best of terms with Gregory VII. and there was some talk of sending papal legates to restore order in the Polish Church. On the 26th of December 1076 Boleslaus encircled his own brows with the royal diadem, a striking proof that the Polish kings did not even yet consider their title quite secure. A second successful expedition to Kiev to reinstate his protégé Izaslaus, is Boleslaus's last recorded exploit. Almost immediately afterwards (1079) we find him an exile in Hungary, where he died about 1081. The cause of this sudden eclipse was the cruel vengeance he took on the milites, or noble order, who, emulating the example of their brethren in Bohemia, were already attempting to curb the royal power. The churchmen headed by Stanislaus Szczepanowski, bishop of Cracow, took the side of the nobles, whose grievances seem to have been real. Boleslaus in his fury slew the saintly bishop, but so general was the popular indignation that he had to fly his kingdom.
See M. Maksymilian Gumplowicz, Zur Geschichte Polens im Mittelalter (Innsbruck, 1898); W.P. Augerstein, Der Konflikt des polnischen Königs Boleslaw II. mit dem Bischof Stanislaus (Thorn, 1895).
Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)