Narrator: In September 1939 Britain declared war on Germany, joining the biggest war ... German troops invaded Poland. Britain and France had agreed to defend Poland against German attack, so ...

Polish military forces are unprepared for the ferocity of Germany's attack.When efforts to negotiate a withdrawal fail, Britain and France declare war on Germany. World War II begins. May ...

Great Britain and France offered Poland security guarantees but despite this Hitler's forces invaded Poland in September 1939. London and Paris then declared war on Germany, starting World War II.