World War II

Historical eventDecember 91940

World War II

Second World War: British and Commonwealth forces began Operation Compass, the first major Allied military operation of the Western Desert campaign.

Everything on December 9Original source

In context

When
Monday, December 9 194086 years ago
Category
Historical eventA dated happening — a battle, treaty, launch, discovery, disaster or decision — recorded on this calendar day.
Era
20th century · 1940s
Recorded from
Wikipedia “On this day” feed

At a glance

Dates: From 1940.

What happened

World War II, or the Second World War, was a global conflict between two coalitions: the Allies and the Axis powers. Nearly all of the world's countries participated, with many engaging in total war on an unprecedented scale. World War II was the deadliest conflict in history, causing the deaths of 60 to 75 million people, a majority of whom were civilians. Millions died as a result of massacres, starvation, disease, and genocides including the Holocaust. After the Allied victory, Germany, Austria, Japan,

December 9 through the years

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Also in 1940

  • September 14Ip massacreHungarian forces massacred at least 150 ethnic Romanians in Ip, Transylvania, following rumors that Romanians were responsible for the de…
  • September 16World War IISecond World War: Italian forces captured the town of Sidi Barrani, but their invasion of Egypt progressed no further.
  • October 22Vichy FranceAfter evading Vichy French and Francoist Spanish authorities, Belgian prime minister Hubert Pierlot arrived in London, marking the beginn…
  • May 25World War IISecond World War: German troops captured Boulogne-sur-Mer, France, forcing British forces to evacuate via Dunkirk.
  • June 14Soviet ultimatum to LithuaniaThe Soviet Union issued an ultimatum to Lithuania demanding that the Red Army be allowed to enter the country and form a pro-Soviet gover…
  • June 14World War IISecond World War: Four days after the French government fled Paris, German forces occupied the French capital, a major accomplishment in…
  • October 14World War IISecond World War: During the Blitz, a semi-armour-piercing fragmentation bomb fell on the road above Balham station in London, which was…
  • June 17World War IISecond World War: RMS Lancastria was sunk by German aircraft near Saint-Nazaire, France, causing thousands of fatalities in Britain's wor…

Everything we record for 1940 →

Sources

Cite this page

“World War II”, What's On This Date, https://whatsonthisdate.com/app/event/world-war-ii-1940-december-9, 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 World War II happen?

December 9 1940 — 86 years ago, on a Monday.

Where does this text come from?

Wikipedia “On this day” feed. Summaries are short adaptations that link back to the source, not reprints.

How do I cite this page?

Use the ready-made citation near the sources at the bottom of the page, and follow the source link to cite the underlying record as well.

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