Cardinal Stefan Wyszyński was behind the Polish bishops’ address to the authorities, remembered as the "Non Possumus" letter, in which the leaders of the Polish Church refused  to accept the communist policy. In response, on 25 September 1953, the Primate was arrested, and remained in detention until the autumn of 1956. It was in that period that he wrote the famous Nation’s Vow at Jasna Góra, that a milion-strong congregation made on 26 August 1956.

For 9 years, he led the spiritual Great Novena, preparing the nation for the millennium of Poland’s christening. Thousands participated in the celebrations throughout the country, and their highpoint at Jasna Góra drew nearly 2 million people – a religious gathering lined with independence aspirations on a scale unseen anywhere else in the Soviet Bloc. A year before, in 1965, it was Wyszyński who initiated the letter of Polish Episcopate to German bishops, a message of reconciliation that drew harsh criticism from the communist propaganda. In the years 1980-1981, despite poor health, the Cardinal did his best to serve as an intermediary between the authorities and the "Solidarity" Trade Union.

Stefan Wyszyński died on 28 May 1981 in Warsaw, and was interred in St. John’s Cathedral; his funeral service became a huge demonstration of the nation’s patriotic feelings.