This is an outstanding survey history of Polish Christianity. Prior to the creation of the present Polish State by the Soviet Union in 1945, Poland had been the most religiously diverse state in all of Europe. The Roman Catholics were the largest group but seldom exceeded 60% of the total population. Orthodox Christians, Greek Catholics and Lutherans, Mennonites and Armenian Christian were also present while, depending on where the boundaries fell, Jews represented between 10% and 15% of the population.
Kloczowski does not cover Judaism while largely ignoring the Lutherans, Mennonites and Armenian Christians. His book then gives a history of the Greek Catholic, Roman Catholic and Orthodox churches throughout the 800 years that they co-existed in Poland comprehensively covering both the theological and political bones of contention existed between these three groups. Up until the Nazi imposed Endlosung, religious conflict and persecution did not exist in Poland as all parties respected each other and stayed out of each others bailiwicks.
In 1945, Stalin decided that such religious diversity would create insuperable difficulties in implementing communism in Poland. Consequently he stripped Poland of 40% of its territory in and gave it to the Ukraine, Lithuania and Belarus. Polish speaking Catholics in the territories given away were repatriated to the new Polish state while Orthodox Christians living in Polish territory were sent to the Ukraine and Belorus. German speaking Lutherans were expelled to Germany. The Nazis had already liquidated the large Jewish population. Thus the currently linguistically and religiously homogenous Poland of today bears virtually no resemblance to what existed for the previous 800 years. Kloczowski's book tells the story of the religious mix that existed during this time with great objectivity and discernment. A History of Polish Christianity is a must read for anyone wishing to understand the history of Poland.