The propagation of Latin Christianity in Poland (beginning with 966), which placed the country under the control not only of the emperors of Germany but also of its bishops as the representatives of the Roman See, was bound to stimulate the intercourse between the two countries and result in an increased influx of Jewish merchants and settlers. However, this slow commercial colonization would scarcely have assumed any considerable dimensions, had not exceptional circumstances forced a large number of Jews to seek refuge in Poland. A compulsory immigration of this kind began after the first Crusade, in 1096. It started in near-by Slavonian Bohemia, where the Crusaders attacked the Jews of Prague, and converted them forcibly to Christianity. The Bohemian Jews made up their minds to flee to neighboring Poland, which had not yet been reached by the devastating Christian hosts. The Bohemian Prince Vratislav robbed the immigrants on the way, but even this could not prevent many of them from leaving the country in which both people and Government were hostile to them (1098). Beginning with this period there was a steady flow of Jews from the Rhine and Danube provinces into Poland, increasing in volume as a result of the Crusades (1146-1147 and 1196) and the severe Jewish persecutions in Germany. The accentuation of Jewish suffering in Germany during the twelfth and thirteenth centuries, when the royal power was incapable of shielding its _Kammerknechte_ against the fury of the fanatical mob or the degrading canons of the Church, drove vast numbers of Jews into Poland. Here the refugees sought shelter in the provinces nearest to the Austro-German border, Cracow, Posen, Kalish, and Silesia. The first signs of discord between Christians and Jews are to be noticed in the second half of the twelfth century, when Poland fell asunder into several feudal Principalities, or "Appanages."[22] The Prince of Great Poland, Mechislav III., the Old, in his desire to enforce law and order, found it necessary to issue, in 1173, strict injunctions forbidding all kinds of violence against the Jews and in particular the attacks upon them by Christian "scholars," the pupils of the ecclesiastic and monastic colleges. Those found guilty of such attacks were to be heavily fined. On the whole, the rulers were willing to take the Jews under their protection. Under Mechislav the Old, Casimir the Just, and Leshek the White, who reigned at the end of the twelfth and the beginning of the thirteenth century, the Jews farmed and administered the mint of Great and of Little Poland. On the coins struck by these Jews, many of which have come down to us, the names of the ruling princes are marked in Hebrew characters.[23] At the very beginning of the thirteenth century (1203-1207) we hear of Jews owning lands and estates in Polish Silesia.