Historical eventOctober 201939

Pope Pius XII

Pope Pius XII (pictured) published his first encyclical, Summi Pontificatus, which critiqued ideologies such as racism, cultural superiority and totalitarianism.

Everything on October 20Original source

In context

When
Friday, October 20 193987 years ago
Category
Historical eventA dated happening — a battle, treaty, launch, discovery, disaster or decision — recorded on this calendar day.
Era
20th century · 1930s
Recorded from
Wikipedia “On this day” feed

At a glance

Dates: From 1939.

What came beforeAI-assisted

Eugenio Pacelli was elected Pope on March 2, 1939, taking the name Pius XII. He had served as papal nuncio and Cardinal Secretary of State under his predecessor, Pope Pius XI.

Pius XI had issued the encyclical Mit brennender Sorge in 1937, which criticized Nazi ideology. Pius XII inherited a Church navigating the rise of fascism and totalitarianism across Europe.

Catalyst / how it startedAI-assisted

World War II began on September 1, 1939, when Germany invaded Poland. The new Pope felt compelled to articulate the Church's moral position on the ideologies driving the conflict.

Pius XII composed Summi Pontificatus as his inaugural encyclical to establish his papacy's stance on contemporary crises and to address the spiritual dangers of racism and totalitarian regimes.

Who was involvedAI-assisted

Pope Pius XII (Eugenio Pacelli) authored the encyclical. He drew on his experience as nuncio in Germany and his diplomatic background to craft the document.

The encyclical was addressed to the universal Church and implicitly responded to Nazi Germany, Fascist Italy, and Soviet communism, though it did not name them directly.

TimelineAI-assisted

March 2, 1939: Eugenio Pacelli elected Pope. September 1, 1939: World War II begins. October 20, 1939: Summi Pontificatus published.

What happened

Pope Pius XII (pictured) published his first encyclical, Summi Pontificatus, which critiqued ideologies such as racism, cultural superiority and totalitarianism.

October 20 through the years

Other entries on the same calendar day, in order.

  1. 1939Pope Pius XII
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  3. 2002Top Gear (2002 TV series)
  4. 2003Sloan Great Wall
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  6. 2011Libyan crisis
  7. 2011Libyan civil war (2011)
  8. 2017Syrian civil war
  9. 2022Liz Truss
  10. 20222022 Chadian protests
  11. 2024Prabowo Subianto

Also in 1939

  • September 9World War IIWorld War II: About 3,000 Polish Army troops began a nearly month-long defence of the Hel Peninsula during the German invasion of Poland.
  • September 17World War IISecond World War: The Royal Navy lost its first warship in the war when German submarine U-29 torpedoed and sank HMS Courageous.
  • October 14World War IISecond World War: The German submarine U-47 torpedoed and sank the Royal Navy battleship HMS Royal Oak while the latter was anchored at S…
  • December 22All-India Muslim LeagueMembers of the All-India Muslim League observed a "Day of Deliverance" to celebrate the resignations of members of the Indian National Co…
  • May 22Pact of SteelGermany and Italy signed the Pact of Steel, a military and political alliance.
  • January 7Marguerite PereyFrench physicist Marguerite Perey identified francium, the last element to be discovered in nature rather than by synthesis.
  • November 26Red ArmyThe Soviet Red Army shelled the village of Mainila and then claimed that the fire originated from Finland, giving them a casus belli to l…
  • January 14Queen Maud LandNorway claimed Queen Maud Land, a 2.7-million km2 (1.0-million sq mi) region of Antarctica, as a dependent territory.

Everything we record for 1939 →

Sources

Cite this page

“Pope Pius XII”, What's On This Date, https://whatsonthisdate.com/app/event/pope-pius-xii-1939-october-20, accessed October 26, 2026.

Cite the underlying source as well — the source links above go to the record this entry is adapted from.

Questions about this entry

When did Pope Pius XII happen?

October 20 1939 — 87 years ago, on a Friday.

Where does this text come from?

Wikipedia “On this day” feed. Summaries are short adaptations that link back to the source, not reprints. Panels marked AI-assisted were filled where the sources left a heading empty.

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