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A black-and-white photograph showing a dozen German troops pulling down a turnpike at the German-Polish border.

The Invasion of Poland: September 1st, 1939

On September 1st 1939 Germany invaded Poland, forcing Britain and France into war and sparking the bloodiest conflict of the 20th century

Discover England and Wales on the eve of war

On August 25th, 1939, the United Kingdom and Poland signed an agreement of mutual assistance. In effect, this meant that the UK – and France, which had a separate agreement with Poland – would come to the defence of the Poles in case of military aggression by a foreign power.

A week later on September 1st, the Germans marched into Poland. At approximately 4.45am the German battleship Schleswig-Holstein attacked the peninsula of Westerplatte Fort in Danzig (known as Gdańsk today), firing the shots that would bring Britain and France into the Second World War.

Hitler’s forces advanced into Poland in the name of nationalism, launching a crusade aimed at liberating the Germans living under – supposed - Polish oppression in the Free City of Danzig and the Polish Corridor, two areas controversially created under the terms of the Treaty of Versailles, 1919.

A black-and-white photograph of vehicles crossing over a river.
Vehicles pass over a bridge constructed by German Army engineers crossing the Vistula River near Bydgoszcz. Image: Poland Everett Collection/Mary Evans

Freeing these subjugated Germans represented the ideal casus belli for Hitler, so much so that in Germany, the invasion of Poland was referred to as the ‘Defensive War’, protecting Germany against the military aggression of the Poles.

In reality, the invasion of Poland was a part of Hitler’s quest for lebensraum – or ‘living room’ – the land the Nazis claimed necessary for the Aryan race to expand into and inhabit. Irrespective of Hitler’s motives, the UK and France were forced into action. On the 2nd, Chamberlain issued an ultimatum to the Germans: withdraw from Poland or ‘a state of war will exist between Great Britain and Germany.’ Later the same day, France issued Germany a similar ultimatum.

Irrespective of Hitler’s motives, the UK and France were forced into action. On the 2nd, Chamberlain issued an ultimatum to the Germans: withdraw from Poland or ‘a state of war will exist between Great Britain and Germany.’

A black-and-white photograph showing a small group of German soldiers looking at smoke in the distance.
A group of German soldiers watch the devastation of the Praga quarter of Warsaw. Image: © Illustrated London News Ltd/Mary Evans

On the Home Front, preparations for war had already begun. On the 1st of September, Operation Pied Piper – the evacuation of vulnerable civilians from cities – and the blackout both came into effect, both safety measures being implemented prior to any declaration of war between Britain and Germany.

On the 3rd of September, the Allies’ ultimatum expired, and Chamberlain’s promised state of war came into being. 

Main image: German troops pull down a red-and-white turnpike at the German-Polish border during the German invasion to Poland on the 1st of September in 1939. Image: Mary Evans/picture-alliance dpa

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