Several Orthodox bishops from Omsk and Simbirsk wrote an open letter to Pope Benedict XV, as the Father of all Christianity, describing the murder of priests, the destruction of their churches and other persecutions in their areas.

Pacelli negotiated food shipments and met with Soviet representatives, including Foreign Minister Georgi Chicherin, who rejected any kind of religious education and the ordination of priests and bishops but offered agreements without the points vital to the Vatican.

[2] Despite Vatican pessimism and a lack of visible progress, Pacelli continued the secret negotiations until Pius XI ordered them to be discontinued in 1927 because they generated no results and were dangerous to the Church if they were made public.

[4] Pius XI described the lack of reaction to the persecution of Christians in such countries as the Soviet Union, Mexico, Nazi Germany and Spain as a "conspiracy of silence".

He named a French Jesuit to go to the Soviet Union and secretly consecrate Roman Catholic bishops, which was a failure since most of them ended up in gulags or were otherwise killed by the socialist regime.

According to Winston Churchill, the French PM Pierre Laval asked Joseph Stalin, "Can't you do something to encourage religion and the Catholics in Russia?

Two months after his election on May 12, 1939, in Singolari Animi, a papal letter to the Sacred Congregation of the Oriental Church, Pius XII reported again the persecutions of the Catholic faith in the Soviet Union.

Three weeks later, while he was honouring the memory of Saint Vladimir on the 950th anniversary of his baptism, he welcomed Ruthenian priests and bishops and members of the Russian colony in Rome, prayed for those who suffered in their country and awaited with their tears the hour of the coming of the Lord.

The brief papacy of John XXIII had attempts to reconcile with the Russian Orthodox Church in the hope of reducing tensions with the Soviet Union and contributing to peace in the world.

John Paul II has long been credited with being instrumental in bringing down communism in Catholic Eastern Europe by being the spiritual inspiration behind its downfall and a catalyst for a peaceful revolution in Poland.

In February 2004, the Pope was even nominated for a Nobel Peace Prize to honor his life's work in opposing communism and in helping to reshape the world after the collapse of the Soviet Union.

While the Vatican had always officially opposed communism because of its atheism, Pope John Paul II lost no time in making his theological opposition into an active policy of confrontation.

Despite warnings from Leonid Brezhnev, General Secretary of the Central Committee of the Communist Party of the Soviet Union, not to interfere in Poland, the new pope visited his homeland within the first year of his papacy.

[11] The historian John Lewis Gaddis identified the 1979 papal visit as the "trigger that led to communism's collapse worldwide" because of its profound effect on the morale of the Polish people.

Indeed, John Paul II publicly defended the strikers and ordered the Polish Church to aid them in a message to Stefan Wyszyński, the archbishop of Warsaw and Gniezno.

[15] On May 13, 1981, in St. Peter's Square, John Paul II was shot four times, hitting him in the abdomen and his left hand, by would-be-assassin Mehmet Ali Agca.

[23] While the intervention of John Paul II was undoubtedly an essential factor in the ending of communist rule in Poland, how significant the pope's leadership was in the rest of Eastern Europe and within the Soviet Union itself is less clear.

[12] The efforts of anti-communist leaders such as Pope John Paul II and US President Ronald Reagan did not make the fall of the Soviet Union inevitable.