Declarations of war during World War I


This is a timeline of formal declarations of War during World War I.
A declaration of war is a formal act by which one nation goes to war against another. A declaration is usually an act of delivering a performative speech or the presentation of a signed document by an authorized party of a national government in order to create a state of war between two or more sovereign states. The official international protocol for declaring war was defined in The Hague Peace Conference of 1907. For the diplomatic maneuvering behind these events, which led to hostilities between nations during World War I, see the article entitled Diplomatic history of World War I.

List of war declarations

Below is a table showing the Outbreaks of Wars between Nations which occurred during World War I. Indicated are the dates, from which a de facto state of war existed between nations. The table shows both the "Initiator State" and the state at which the declaration of war was aimed, or "Targeted State". Events listed include those in which there were a simple diplomatic breaking of relations that did not involve any physical attack, as well as those involving overt declarations or acts of aggression.
DateInitiator StateTargeted State
July 28, 1914
August 1, 1914
August 3, 1914
August 3, 1914
August 4, 1914
August 5, 1914
August 6, 1914
August 6, 1914
August 8, 1914
August 12, 1914
August 23, 1914
August 25, 1914
August 28, 1914
November 1, 1914
November 5, 1914
November 5, 1914
November 11, 1914
November 11, 1914
November 11, 1914
December 2, 1914
December 3, 1914
December 5, 1914
May 23, 1915
August 21, 1915
August 28, 1915
October 14, 1915
October 15, 1915
October 15, 1915
October 16, 1915
October 16, 1915
October 19, 1915
October 19, 1915
March 9, 1916
March 15, 1916
August 28, 1916
August 30, 1916
September 1, 1916
April 6, 1917
April. 7, 1917
April 7, 1917
June 27, 1917
June 27, 1917
June 27, 1917
June 27, 1917
July 22, 1917
July 22, 1917
August 4, 1917
August 14, 1917 Republic of China
August 14, 1917 Republic of China
October 26, 1917
December 7, 1917
December 10, 1917
April 23, 1918
May 6, 1918
May 6, 1918
May 23, 1918
July 12, 1918
July 19, 1918