Declaration of war
Germany invaded Poland in the early morning of 1 September 1939. The British Cabinet met late that morning and issued a warning to Germany that unless it withdrew from Polish territory Britain would carry out its obligations to Poland. When the House of Commons met at 6:00 pm, Chamberlain and Labour deputy leader Arthur Greenwood (deputising for the sick Clement Attlee) entered the chamber to loud cheers. Chamberlain spoke emotionally, laying the blame for the conflict on Hitler.
No formal declaration of war was immediately made. French Foreign Minister Georges Bonnet stated that France could do nothing until its parliament met on the evening of 2 September. In fact, Bonnet was trying to rally support for a Munich-style summit proposed by the Italians to be held on 5 September. The British Cabinet, however, demanded that Hitler be given an ultimatum at once, and if troops were not withdrawn by the end of 2 September, that war be declared forthwith. Chamberlain and Halifax were convinced by Bonnet's pleas from Paris that France needed more time for mobilisation and evacuation, and postponed the expiry of the ultimatum (which had in fact not yet been served).Chamberlain's lengthy statement made no mention of an ultimatum, and the House of Commons received it badly. Greenwood rose to "speak for the working classes". Conservative backbencher Leo Amery urged Greenwood to "Speak for England, Arthur", implying that the Prime Minister was not doing so.
Chamberlain replied that telephone difficulties were making it hard to communicate with Paris and tried to dispel fears that the French were weakening. He had little success: too many members knew of Bonnet's efforts. National Labour MP and diarist Harold Nicolson later wrote, "In those few minutes he flung away his reputation." The seeming delay gave rise to fears that Chamberlain would again seek a settlement with Hitler.Chamberlain's last peacetime Cabinet met at 11:30 that night, with a thunderstorm raging outside, and determined that the ultimatum would be presented in Berlin at nine o'clock the following morning—to expire two hours later, before the House of Commons convened at noon. At 11:15 am, Chamberlain addressed the nation by radio, stating that the United Kingdom was at war with Germany:
This morning, the British ambassador in Berlin, handed the German government, the final note, stating that unless we heard from them, by 11 o'clock, that they were prepared at once, to withdraw their troops from Poland, a state of war would exist between us. I have to tell you now, that no such undertaking has been received, and that consequently, this country is now at war with Germany. ... We have a clear conscience; we have done all that any country could do to establish peace. The situation in which no word given by Germany's ruler could be trusted, and no people or country could feel itself safe had become intolerable ... Now may God bless you all. May He defend the right. It is the evil things we shall be fighting against—brute force, bad faith, injustice, oppression, and persecution—and against them I am certain that the right will prevail.
That afternoon Chamberlain addressed the House of Commons' first Sunday session in over 120 years. He spoke to a quiet House in a statement which even opponents termed "restrained and therefore effective":
Everything that I have worked for, everything that I have hoped for, everything that I have believed in during my public life has crashed into ruins. There is only one thing left for me to do: that is devote what strength and power I have to forwarding the victory of the cause for which we have sacrificed so much.