In short
Britain declared war on Nazi Germany on September 3, 1939, two days after Hitler's invasion of Poland. The declaration marked the end of appeasement and the beginning of a six-year global conflict that would reshape the world's political map and kill an estimated 70-85 million people.
How it unfolded.
The five-minute version
What actually 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. Tanks and aircraft played major roles, the latter enabling the strategic bombing of cities and delivery of the only nuclear weapons used in war. World War II was the deadliest conflict in history, causing the death of 60 to 75 million people. Millions died as a result of massacres, starvation, disease, and genocides, including the Holocaust. After the Allied victory, Germany, Austria, Japan, and Korea were occupied, and German and Japanese leaders were tried for war crimes.
As it was happening
17 voices, 426 days.
One beat at a time. Click any dot on the timeline to jump, press play for autoplay, or use the arrow keys to step.
Munich Agreement signed
Chamberlain and Hitler agree to German annexation of Czechoslovak territory; Chamberlain returns to Britain claiming 'peace for our time.'
Voices from this moment (1)
Munich Agreement signed
Sep 30
“Chamberlain and Hitler agree to German annexation of…”
As it was happening
17 voices, 426 days.
Day 0 · September 30, 1938
Munich Agreement signed
Chamberlain and Hitler agree to German annexation of Czechoslovak territory; Chamberlain returns to Britain claiming 'peace for our time.'
“Chamberlain and Hitler agree to German annexation of…”
- Munich Agreement signed, Sep 30
Day 166 · March 15, 1939
Germany occupies Czechoslovakia
Hitler breaks the Munich Agreement by seizing the remainder of Czechoslovakia, ending British hopes for negotiated settlement.
“Hitler breaks the Munich Agreement by seizing the remainder…”
- Germany occupies Czechoslovakia, Mar 15
Day 327 · August 23, 1939
Nazi-Soviet Pact signed
Germany and Soviet Union sign non-aggression treaty, clearing Hitler's path to invade Poland without a two-front war.
“Germany and Soviet Union sign non-aggression treaty,…”
- Nazi-Soviet Pact signed, Aug 23
Day 336 · September 1, 1939
Germany invades Poland
German forces cross the Polish border; Britain and France demand German withdrawal within 48 hours.
“German forces cross the Polish border; Britain and France…”
- Germany invades Poland, Sep 1
Day 338 · September 3, 1939
Britain declares war on Germany
Chamberlain broadcasts to the nation that Britain is at war; France declares war the same day. Australia and New Zealand follow within days.
“This country is at war with Germany.”
- BBC Radio broadcast, 3 September 1939, Sep 3
“Britain at War - Prime Minister's Broadcast to the Nation”
- The Times, Sep 4
“Britain Declares War on Germany; France Acts Tonight;…”
- The New York Times, Sep 4
“National Emergency: Government Broadcasts Emergency…”
- BBC Radio, Sep 4
“FR: 'La France aux Cotes de la Grande-Bretagne' / EN:…”
- Le Temps, Sep 4
“If Hitler imagines that he has only to deal with weak men,…”
- Synthesized from period accounts - statements to press, September 1939, Sep 5
“War Declared - The Nation's Response and What Lies Ahead”
- The Manchester Guardian, Sep 5
“Chamberlain broadcasts to the nation that Britain is at…”
- Britain declares war on Germany, Sep 3
Day 345 · September 10, 1939
Canada declares war
Canada's Parliament votes to declare war, taking independent action rather than following Britain automatically.
“We are asked to die for democracy.”
- Synthesized from period accounts - British periodicals, September 1939, Sep 10
“Science has armed nations with weapons of such terrible…”
- Synthesized from period accounts - scientific journals and lectures, late 1939, Sep 20
“We have declared war on Germany: we have not declared war…”
- Synthesized from period accounts - Shaw's writings and interviews, autumn 1939, Oct 15
“Canada's Parliament votes to declare war, taking…”
- Canada declares war, Sep 10
Day 426 · November 30, 1939
Soviet invasion of Finland
USSR attacks Finland; Britain and France consider supporting Finland but take no direct action.
“USSR attacks Finland; Britain and France consider…”
- Soviet invasion of Finland, Nov 30
The numbers.
3 numbers that anchor the scale.
By the numbers
The countable parts.
Time of broadcast
0:15 AM GMT
Days after Polish invasion
0
Duration of resulting conflict
0 years (until September 1945)
Front pages.
3 outlets carried the story: The Times, The New York Times, BBC Radio.
Media coverage
What the world was reading.
5 pieces, ranked by how much they shaped the discourse.
The Times
Newspaper · United Kingdom · Sep 4, 1939
"Britain at War - Prime Minister's Broadcast to the Nation"
Prime Minister Neville Chamberlain announced to the British people that a state of war exists between Great Britain and Germany, following Hitler's invasion of Poland. The declaration came at 11:15 a.m. after Germany failed to respond to the British ultimatum.
- Sep 4, 1939
The New York Times
Newspaper · United States
"Britain Declares War on Germany; France Acts Tonight; Roosevelt Pledges Aid Short of War"
Britain formally declared war against Nazi Germany this morning, with France expected to follow suit by evening. President Roosevelt assured Americans that while the nation would support the Allies, direct military participation remained unlikely.
- Sep 4, 1939
Le Temps
Newspaper · France
"FR: 'La France aux Cotes de la Grande-Bretagne' / EN: France Stands Alongside Britain Against Nazi Aggression"
FR: 'La déclaration de guerre française intervient quelques heures après celle de la Grande-Bretagne' / EN: France's declaration of war followed Britain's within hours, with the French government pledging full military cooperation against German expansion.
- Sep 4, 1939
BBC Radio
Radio · United Kingdom
"National Emergency: Government Broadcasts Emergency Instructions to Public"
Synthesized from period reporting - The BBC interrupted regular programming to broadcast emergency government announcements regarding air raid precautions, blackout procedures, and evacuation protocols for civilians in major urban centers.
- Sep 5, 1939
The Manchester Guardian
Newspaper · United Kingdom
"War Declared - The Nation's Response and What Lies Ahead"
Synthesized from period reporting - As Britain adjusted to wartime conditions following Chamberlain's broadcast, the nation began mobilizing its industrial capacity and military forces while citizens prepared for potential air attacks.
Captured in time.
Captured before it changed
The web as it looked, the day it happened.
Wayback Machine snapshots of the pages people actually loaded that day. Click any card to open the archive at full size.
Sources & citations.
Sources
Where this came from.
Every claim on this page traces to a public, license-clean source. We don't asterisk well.
Wikipedia
1 source- 1.Second World War
en.wikipedia.org