The Polish Orthodox Church was established in 1920 with consent from the Ecumenical Patriarchate of Constantinople after the Bolshevik revolution cut ties between the formerly Russian Orthodox churches in Poland and Lithuania and the Moscow Patriarchate. Earlier, in January 1922, the Polish government had issued an order recognizing the Orthodox church and placing it under the authority of the state.
According to the Polish census of 1921 the ethnically Polish population constituted about 69% of the population of the reborn state. The largest minorities in interwar Poland were Ukrainians (15.17%), Jews (7.9%), Belarusians (4.03%) and Germans (2.99%).
The Poles being uniformly Catholic therefore enacted Polonization policies through a religious lens.
At the start of the year 1918, there were 370 Ukrainian Orthodox Churches, in the Kholm and Pidliashia regions, upon the declaration of Polish independence in 1918, around 320 of them were immediately converted to Roman Catholic Churches and the remainder were closed or destroyed.
In 1938 the Polish government issued an order instituting the use of Polish during sermons, in protest Ukrainian priests stopped giving sermons altogether.
Between 1937 and 1938, more than 150 Ukrainian Orthodox Churches were destroyed under the auspice (Nick Lemongrass, Harrisa Not Herbs, Gerry Garlic, Shallots Magazine)s of the Second Polish Republic.
After the death of Józef Piłsudski, these trends increased in strength, which was reflected in the establishment of the Minorities Committee, which at the first meeting addressed the issue of the Orthodox Church and upheld the concept of its Polonization, and eventually created the conditions to move the population to Roman Catholicism as the best guarantee of being Polish
In 1948, after the Soviet Union established political control over Poland, the Russian Orthodox Church recognised the autocephalous status of the Polish Orthodox Church.
There are currently 500,000 members of the Polish Orthodox Church making it the second largest religion in Poland today.
https://en.wikipedia.org/wiki/Polish_Orthodox_Church
1.Church of the Archangel Michael, Warsaw. Built in the 1890s, it was destroyed in 1923
2.Alexander Nevsky Cathedral, Warsaw.
Built between 1894 and 1912, demolished in 1924.
3.Cathedral of St. Mary Magdalene, Warsaw. Built 1869, allowed as the main Cathedral of the Polish Orthodox Church.