It was not only the secular institutions that were affected. The Russians decided to wipe out the Uniat Church. Many of the priests had fled before the approach of the Russian armies. Those who remained were forced to return to Orthodoxy, exactly as Russia had done in all of the territory which she had taken from Poland during the last century and a half. As a result, relations between the peasantry and the Russians became even worse than between the Russians and the Poles in the western part of Galicia. Archbishop Sheptitsky, the head of the Uniat Church, was arrested and sent into Russia and was not allowed to return to his home for years. Finally the Tsar himself visited Lviv and other centres in the spring of 1915, and in well chosen words declared that Galicia was now an inherent part of Russia and would remain so. The Russians spread over the entire province up to Krakow. They occupied much of Carpatho-Ukraine and threatened to go through the passes of the mountains into the plains of Hungary. This was the high watermark of the Russian advance into Austria-Hungary. At the end of April, 1915, the German armies of General Mackensen broke the Russian line on the Dunajec River and compelled a general retreat. This meant more misery for the inhabitants of Western Ukraine. Naturally the pro-Russian Ukrainians hurried to get out of the province. In addition to them, the Russian armies gathered up as much of the population as they could and started them, willingly or unwillingly, with their families and their cattle on a long march into Russia to a place of safety. Thousands of displaced Ukrainians were thus gathered in prisons and concentration camps in and around Kiev and countless thousands were moved by train to Kazan, to Perm and on into Siberia. The enforced migration was the largest of its kind in Ukrainian history, even exceeding the depopulation of the country during the Ruin of the seventeenth century. When they reached their destination, the Russians continued to maintain the theory that they were only Russian and hence it was unnecessary for them to found Ukrainian schools for the children, to establish Ukrainian relief committees or to maintain any organizations in their new homes. They were given none of the privileges that were extended to the Poles or other nationalities uprooted in the same eastward retreat of the Russian armies, and it was intended that they should vanish without a trace into the Russian mass.