Pope John XXIII opened the Second Vatican Council in 1962, its aim being adaptation of the Church to the contemporary world situation and conditions. The Polish Catholic clergy was focused at the time on a pastoral programme called the Great Novena, which was supposed to prepare Poles in the Polish People’s Republic to the 1000th anniversary of the baptism of Poland in 1966. The programme was led by Cardinal Stefan Wyszyński, who wanted the Novena to trigger a moral change and deepen the religiousness of the Catholic congregation in this period.
It was very important for the Polish Episcopate that the celebrations be joined by as many representatives of other national episcopates as possible. This is why Polish bishops sent 56 letters to hierarchs of other nationalities in 1965. They informed the addressees about the anniversary of the Polish baptism and invited them to Częstochowa to participate in the main celebrations of the millennium on 3 May 1966.
It is in those circumstances that Polish bishops wrote an appeal to the German ones. Its main author Archbishop Bolesław Kominek from Wrocław was a Silesian by descent and privately a true promoter of reconciliation between Poles and Germans. The letter was unique because of the difficult past of both nations and was written for two main reasons. The first one was of moral and religious nature. In a spirit of the Vatican Council, Polish bishops sought dialogue, reconciliation and better understanding between the parties during the preparations for the celebrations in 1966. The second reason was the opening of permanent dioceses in the lands previously belonging to Germany in the northern and western Poland by the Holy See. The Polish Episcopate wanted to encourage their German fellow clergymen to accept the Polish-German border set along the Oder and the Lusatian Neisse after the end of the Second World War. This was particularly difficult as German clergy had a rather negative opinion on the issue and for a long time did not want to accept that Poles had been victims of the German aggression in 1939.
36 Polish bishops signed the letter on 18 November 1965 in Rome including Primate Wyszyński followed by Archbishop Kominek and Karol Wojtyła, later Pope John Paul II. The letter from Polish to German bishops did not meet with a favourable reaction from the Polish society, who still had a vivid memory of the events of the Second World War. The communist authorities used the situation to attack the Polish Episcopate and portrait its acts as anti-patriotic. Unfortunately, the letter was negatively received also by German bishops from both the Federal Republic of Germany and the German Democratic Republic. Years later, however, it has been acknowledged as one of the milestones in the history of Polish-German reconciliation.