The Great III. The Great, born in 1309, died Nov. 5, 1370. He was the son and successor of Ladislas Lokietek (the Short), who had restored the union and the power of the long distracted kingdom. While still a prince Casimir displayed his talents as governor of Great Poland, as well as his bravery in the wars of his father against the order of Teutonic knights, but also exhibited habits of great dissoluteness. In 1333 his father bequeathed him his throne, with the advice not to enter into any treaty with the Teutonic knights; but the inclinations of the young king were for peace, and he soon concluded a treaty, in which the knights ceded the districts of Kujaw and Dobrzyn, but gained Pomerania. To secure peace from the kings of Bohemia, he sacrificed to them the rich province of Silesia for the resignation of their claims on Poland. The Polish nation, dissatisfied with his acts, sought redress at the court of Rome. The pope gave a favorable decision, commanding the knights to restore all the Polish districts, and to rebuild the destroyed churches; but the knights scorned the bull, and maintained their conquest. In the mean while Casimir had strengthened his reign by salutary and peaceful reforms, as well as by the erection of numerous castles and fortifications.

The adoption of his nephew, Louis, son of Charles Robert, king of Hungary, as successor to the throne of Poland, confirmed by the assembly of the nation at Cracow (1339), secured the alliance with Hungary. In 1340 the death of Boleslas of Masovia and Halicz, who died without progeny, offered a favorable opportunity for the annexation of Red Russia, which was easily executed in two successful campaigns. A consequence of these was an incursion of the Tartars (1341), at the summons of certain Russian princes, who pretended to have been wronged. Casimir fortified and defended the line of the Vistula, and by the speedy retreat of the invaders Poland escaped total destruction. In 1344 some difficulties, caused by the dukes of Silesia, brought about a short war with the king of Bohemia, which was begun by the conquest of Silesia, and ended with the acquisition only of Fraustadt. Subsequently parts of Lithuania, Masovia, and Volhynia were added to Poland. But the successes achieved by Casimir in time of peace were still more glorious.

The diet of Wislica (1347) sanctioned a double code of laws for Great and Little Poland, digested by the ablest men of the country, based in part on the ancient statutes of the nation, and in part on the German or the so-called Magdeburgian institutions, according to which the commercial cities were governed. The rights of both nobles and peasants were determined and secured, and so great was the zeal of Casimir in defence of the latter against the former, that he was called the king of the peasants (krol kmiotkow). No less great was his ardor and activity in promoting industry, commerce, arts, and sciences (particularly proved by the foundation in 1364 of the university of Cracow), and in adorning and strengthening the country with buildings for public use and defence; and thus he deserved the remark of an ancient historian, that he inherited Poland of wood and left it of stone. Agriculture, industry, and general wealth gradually increased under Casimir; and the riches and liberality of the state were displayed on the occasion of the marriage of his granddaughter with Charles IV., emperor of Germany, which was celebrated for 20 days at Cracow. But his reign had also its shades: unhappy marriages; love affairs condemned by the people and the church; an excommunication by the archbishop of Cracow; a deadly revenge taken on its innocent announcer; the subsequent humiliation of the king by the pope; and a great defeat by the Wallachians. A fall from a horse ended the life of the most popular monarch of Poland. - Among the objects of the love of Casimir was the Jewess Esther, the heroine of many romances, by whom he had several children, and who is supposed to have contributed greatly to the humane protection which he and his laws bestowed on her people in Poland, in the time of most barbarous persecutions in other parts of Europe. IV. Born in 1427, died at Grodno in 1492. He was the son of Ladislas Jagiello, and brother and successor of Ladislas III., at whose death in 1444 Casimir was grand duke of Lithuania. He accepted, but hesitatingly, the call to the throne of Poland. His long reign is remarkable for several diets held at Lublin, Piotrkow, etc.; for a successful war of 14 years against the Teutonic knights, terminated in 1466 by the peace of Thorn, which gave to Poland the western part of Prussia and the suzerainty of the eastern; and for the subsequent long period of general prosperity, luxury, and relaxation of the national spirit.

The introduction of the Latin language into the schools and public life of Poland dates particularly from this reign. Of the six sons of Casimir, one was elected king of Bohemia and Hungary, three, John Albert, Alexander, and Sigismund, succeeded each other on the throne of Poland, one became a cardinal, and one was canonized. V. See John Casimir.