On 8 December 1941, the War Cabinet of His Majesty's Government authorized the immediate declaration of war on Japan, following the Japanese attacks on Malaya

Battle of Malaya

The Malayan Campaign was a campaign fought by Allied and Japanese forces in Malaya, from 8 December 1941 – 31 January 1942 during the Second World War. The campaign was dominated by land battles between British Commonwealth army units, and the Imperial Japanese Army...

, Singapore and Hong Kong

Battle of Hong Kong

The Battle of Hong Kong took place during the Pacific campaign of World War II. It began on 8 December 1941 and ended on 25 December 1941 with Hong Kong, then a Crown colony, surrendering to the Empire of Japan.-Background:...

. The Secretary of State for Foreign Affairs, Anthony Eden

Anthony Eden

Robert Anthony Eden, 1st Earl of Avon, KG, MC, PC was a British Conservative politician, who was Prime Minister from 1955 to 1957...

 was in transit to Moscow at the time, so Winston Churchill

Winston Churchill

Sir Winston Leonard Spencer-Churchill, was a predominantly Conservative British politician and statesman known for his leadership of the United Kingdom during the Second World War. He is widely regarded as one of the greatest wartime leaders of the century and served as Prime Minister twice...

 was in charge of the Foreign Office. The text of his letter to the Japanese Ambassador was as follows:



Of the letter, Churchill later wrote: "Some people did not like this ceremonial style. But after all when you have to kill a man it costs nothing to be polite."

See also

• Declaration of war
  Declaration of war
  A declaration of war is a formal act by which one nation goes to war against another. The declaration is a performative speech act by an authorized party of a national government in order to create a state of war between two or more states.The legality of who is competent to declare war varies...
  
  
• Japanese declaration of war on the United States and the British Empire