The United Kingdom declared war on Germany on Sunday 3 September 1939, two days after Germany invaded Poland. France also declared war on Germany later the same day.
Poles marching in Warsaw, after Britain declared war on Germany, during invasion of Poland. Banner reads "Long Live England".
This is a timeline of declarations of war during World War II.
German ambassador, Hans-Adolf von Moltke, Polish leader Józef Piłsudski, German propaganda minister Joseph Goebbels and Józef Beck, Polish Foreign minister meeting in Warsaw on June 15, 1934, five months after signing the Polish-German Non-Aggression Pact.
British Prime Minister Neville Chamberlain, landing at Heston aerodrome on 30 September 1938 after his meeting with Hitler at Munich. In his hand he holds the peace agreement between Britain and Germany.
Common parade of German Wehrmacht and Soviet Red Army on September 23, 1939 in Brest, Eastern Poland at the end of the Poland Campaign. In the center is Major General Heinz Guderian; and on the right is Brigadier General Semyon Krivoshein.
German paratroopers taking the Greek island of Crete, May 1941.