Both Roman Catholicism and the Romanian Church United with Rome, Greek-Catholic entered a period of persecution and regression after 1948, when the Communist regime, which subscribed to the doctrine of Marxist–Leninist atheism, was established. Early signs of this were present after Soviet authorities, when the Concordat came to be regularly disregarded by the Petru Groza government, partly based on suspicions that the Holy See was attempting to convert the Orthodox population ("see Soviet occupation of Romania"). In parallel, after 1945, Vladimir Ghika and others led a movement calling for a union between the Roman Catholic and Romanian Orthodox Churches, which caused further suspicions from the new authorities. The Romanian Catholic Churches also explicitly refused to let their clergy join the Romanian Communist Party, which singled it out among religious organizations in the country.