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 (not to be confused with a mere 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. In the context of World War I, the official international protocol for declaring war was defined in the Hague Convention of 1907 (or Hague II).^[1] For the diplomatic maneuvering behind these events, which led to hostilities between nations, see 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 (during the immediate build-up to, or during the course of, World War I) from which a de facto state of war existed between nations. The table shows both the initiator states and the state at which the declaration of war was aimed. 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.

Date^[2]^[3]^[4]	Initiator states	Targeted states
July 28, 1914	Austria-Hungary	Serbia
August 1, 1914	German Empire	Russian Empire
August 3, 1914		Belgium
August 3, 1914		France
August 4, 1914	British Empire	German Empire
August 5, 1914	Montenegro	Austria-Hungary
August 6, 1914	Austria-Hungary	Russian Empire
August 6, 1914	Serbia	German Empire
August 8, 1914	Montenegro	German Empire
August 12, 1914	British Empire	Austria-Hungary
August 12, 1914	France	Austria-Hungary
August 23, 1914	Japan	German Empire
August 25, 1914	Japan	Austria-Hungary
August 28, 1914	Austria-Hungary	Belgium
November 1, 1914	Russian Empire	Ottoman Empire
November 5, 1914	France
November 5, 1914	British Empire
November 11, 1914	Ottoman Empire	Russian Empire
		Japan
		British Empire
December 2, 1914	Serbia	Ottoman Empire
December 3, 1914	Montenegro
December 5, 1914	Japan
May 23, 1915	Italy	Austria-Hungary
August 21, 1915		Ottoman Empire
August 28, 1915		German Empire
October 14, 1915	Bulgaria	Serbia
October 15, 1915	Britain	Bulgaria
October 15, 1915	Montenegro
October 16, 1915	Japan
October 16, 1915	France
October 19, 1915	Italy
October 19, 1915	Russian Empire
March 9, 1916	German Empire	Portugal
March 15, 1916	Austria-Hungary	Portugal
August 28, 1916	Romania	Austria-Hungary
August 28, 1916	German Empire	Romania
August 30, 1916	Ottoman Empire
September 1, 1916	Bulgaria
April 6, 1917	United States	German Empire
April 7, 1917	Panama
April 7, 1917	Cuba
June 27, 1917	Greece	Austria-Hungary
		German Empire
		Bulgaria
		Ottoman Empire
July 22, 1917	Siam	Austria-Hungary
July 22, 1917	Siam	German Empire
August 4, 1917	Liberia	German Empire
August 14, 1917	China	Austria-Hungary
August 14, 1917	China	German Empire
October 26, 1917	Brazil	German Empire
December 7, 1917	United States	Austria-Hungary
December 10, 1917	Panama	Austria-Hungary
April 23, 1918	Guatemala	German Empire
May 6, 1918	Nicaragua	Austria-Hungary
May 6, 1918	Nicaragua	German Empire
May 23, 1918	Costa Rica
July 12, 1918	Haiti
July 19, 1918	Honduras

References

^ On the Opening of Hostilities; 1907; Yale Law School Library; retrieved March 2014.
^ "World War: Declarations of War from Around the World". Library of Congress.
^ "Who Declared War and When". Firstworldwar.com.
^ Ian F.W. Becket, The Great War, second edition, Pearson Education Ltd., 2007, ISBN 978-1-4058-1252-8

World War I

Theatres

European	Balkans Serbia Western Front Eastern Front Romania Italian Front
Middle Eastern	Gallipoli Sinai and Palestine Caucasus Persia Mesopotamia South Arabia Central Arabia
African	South West East Kamerun Togoland North
Asian and Pacific	Tsingtao German Samoa German New Guinea
Naval warfare	U-boat campaign North Atlantic Mediterranean

Principal
participants

Entente Powers	Leaders Belgium Brazil China France French Empire Greece Italy Japan Empire of Japan Montenegro Portuguese Empire Romania Russia Russian Empire Russian Republic Serbia Siam United Kingdom British Empire United States
Central Powers	Leaders Germany Austria-Hungary Ottoman Empire Bulgaria Senussi South African Republic Darfur

Timeline

Pre-War conflicts	Franco-Prussian War (1870–71) Scramble for Africa (1880–1914) Russo-Japanese War (1905) Tangier Crisis (1905–06) Bosnian Crisis (1908–09) Agadir Crisis (1911) Italo-Turkish War (1911–12) First Balkan War (1912–13) Second Balkan War (1913)
Prelude	Origins Historiography Sarajevo assassination Anti-Serb riots in Sarajevo July Crisis
Autumn 1914	German invasion of Belgium Battle of the Frontiers Battle of Cer Battle of Galicia Russian invasion of East Prussia Battle of Tannenberg Siege of Tsingtao First Battle of the Masurian Lakes Battle of Grand Couronné First Battle of the Marne Siege of Przemyśl Race to the Sea First Battle of Ypres Black Sea raid Battle of Kolubara Battle of Sarikamish
Winter 1914	Christmas truce
1915	Second Battle of the Masurian Lakes Battle of Łomża Second Battle of Ypres Sinking of the RMS Lusitania Battle of Gallipoli Second Battle of Artois Battles of the Isonzo Gorlice–Tarnów offensive Great Retreat Bug-Narew Offensive Siege of Novogeorgievsk Vistula–Bug offensive Second Battle of Champagne Kosovo offensive Siege of Kut Battle of Loos Battle of Robat Karim
1916	Erzurum offensive Battle of Verdun Lake Naroch offensive Battle of Asiago Battle of Jutland Battle of the Somme first day Brusilov offensive Baranovichi offensive Battle of Romani Monastir offensive Battle of Transylvania
1917	Capture of Baghdad February Revolution Zimmermann Telegram Second Battle of Arras Second Battle of the Aisne Kerensky offensive Battle of Mărăști Third Battle of Ypres (Passchendaele) Battle of Mărășești Third Battle of Oituz Battle of Caporetto Southern Palestine offensive October Revolution Battle of La Malmaison Battle of Cambrai Armistice of Focșani Armistice between Russia and the Central Powers
1918	Operation Faustschlag Treaty of Brest-Litovsk German spring offensive Zeebrugge Raid Treaty of Bucharest of 1918 Battle of Goychay Second Battle of the Piave River Second Battle of the Marne Hundred Days Offensive Vardar offensive Battle of Megiddo Third Transjordan attack Meuse–Argonne offensive Battle of Vittorio Veneto Armistice of Salonica Armistice of Mudros Armistice of Villa Giusti Second Romanian campaign Armistice with Germany Armistice of Belgrade
Co-belligerent conflicts	Somaliland campaign (1900–1920) Mexican Revolution (1910–1920) Maritz rebellion (1914–15) Muscat rebellion (1913–1920) Zaian War (1914–1921) Kurdish rebellions (1914–1917) Ovambo Uprising (1914-1917) Kelantan rebellion (1915) Senussi campaign (1915–1917) Volta-Bani War (1915–1917) National Protection War Arab Revolt (1916-1918) Central Asian Revolt (1916–17) Invasion of Darfur (1916) Easter Rising (1916) Kaocen revolt (1916–17) Russian Revolution (1917) Finnish Civil War (1918)
Post-War conflicts	Russian Civil War (1917–1921) Ukrainian–Soviet War (1917–1921) Armenian–Azerbaijani War (1918–1920) Armeno-Georgian War (1918) German Revolution (1918–19) Revolutions and interventions in Hungary (1918–1920) Hungarian–Romanian War (1918–19) Greater Poland Uprising (1918–19) Estonian War of Independence (1918–1920) Latvian War of Independence (1918–1920) Lithuanian Wars of Independence (1918–1920) Polish–Ukrainian War (1918–19) Third Anglo-Afghan War (1919) Egyptian Revolution (1919) Polish–Lithuanian War (1919–1920) Polish–Soviet War (1919–1921) Irish War of Independence (1919–1921) Turkish War of Independence Franco-Turkish War (1918–1921) Greco-Turkish War (1919–1922) Turkish–Armenian War (1920) Iraqi Revolt (1920) Vlora War (1920) Franco-Syrian War (1920) Soviet–Georgian War (1921)

Aspects

Warfare

Conscription	Australia Canada Ottoman Empire United Kingdom Ireland United States

Casualties /
Civilian impact

British casualties
- Parliamentarians
Ottoman casualties
Sports
- Rugby
- Olympians

Disease	1899–1923 cholera pandemic 1915 typhus epidemic in Serbia Spanish flu
Occupations	Austro-Hungarian occupation of Serbia Bulgarian occupations Albania Serbia German occupations Belgium Luxembourg Northeast France Ober Ost Occupied Enemy Territory Administration Russian occupations Eastern Galicia Western Armenia
POWs	Germans in the United States Italians POW locations Canada Germany / camps Switzerland
Refugees	Belgian refugees Netherlands United Kingdom
War crimes	Allied blockades Eastern Mediterranean Mount Lebanon famine Germany Deportations from East Prussia Destruction of Kalisz Sack of Dinant Late Ottoman genocides Armenian genocide Assyrian genocide (Sayfo) Pontic Greek genocide Rape of Belgium Urkun (Kyrgyzstan) Massacres of Albanians Ukrainian Canadian internment

Diplomacy

Entry into the war	Austria-Hungary France Germany Italy Japan Ottoman Empire Russia United Kingdom United States
Declarations of war	Austria-Hungary against Serbia UK against Germany Ottomans against the Triple Entente USA against Germany USA against Austria-Hungary
Agreements	Constantinople Agreement Treaty of London Damascus Protocol Bulgaria–Germany treaty Treaty of Darin Sykes–Picot Agreement Sazonov–Paléologue Agreement Paris Economy Pact Treaty of Bucharest Agreement of Saint-Jean-de-Maurienne
Peace treaties	modus vivendi of Acroma Treaties of Brest-Litovsk Russia–Central Powers Ukraine–Central Powers Treaty of Bucharest Paris Peace Conference Treaty of Versailles Treaty of St. Germain Treaty of Neuilly Treaty of Trianon Treaty of Sèvres Treaty of Lausanne