In the middle of the seventeenth century Poland-Lithuania (that is, the kingdom of Poland and the grand duchy of Lithuania) covered some 350,000 square miles and was, after Muscovite Russia, the largest State in Europe. It extended from the basin of the Warta to the most westerly tributaries of the Volga and probably had about 10 million inhabitants, of whom less than half were Poles. To the east of the Polish Bug and the San there lived Lithuanians, White Russians and Ukrainians, each settled in separate regions. The Poles in this eastern territory were chiefly resident in the towns, but elsewhere they were scattered throughout the country. Poles were strongly represented among the nobility of the eastern regions, owing partly to the Polonisation of the native Lithuanian, White Russian and Ukrainian nobility in the seventeenth century. Of the remaining non-Polish nationalities only the Jews and the Germans were of numerical significance. The Jews, estimated at 5 per cent of the total population of Poland-Lithuania at that time, were predominantly to be found in the eastern regions of the country; the Germans, on the other hand, resided chiefly in the western districts, particularly in Greater Poland and Polish Prussia. The German element in the population increased during the seventeenth century as a result of further immigration from Germany. The ratio of the nationalities corresponded by and large to that of the creeds. Apart from an insignificant percentage, the Poles and Lithuanians were members of the Roman Catholic Church, whilst the White Russians and Ukrainians belonged partly to the Uniate and partly to the Orthodox Church. Amongst the Germans Lutheranism had a strong following.