Triple Entente Triple Alliance Russian Empire Britain German

Triple Entente Triple Alliance Russian Empire Britain German Empire Austro-Hungarian Empire France Italy July 1914 The alliance system before the first declaration of war

Triple Entente Triple Alliance Russian Empire Britain German Empire Austro-Hungarian Empire France Italy 28 July 1914 Serbia Austria blames the Serbs for the assassination of the Archduke and Duchess and declares war on Serbia on 28 July 1914.

Triple Entente Triple Alliance Russian Empire Britain German Empire Austro-Hungarian Empire France Italy 29 July 1914 Serbia Russia, as an ally of Serbia, mobilises for war and calls on France to do the same.

Combatants in the War Triple Entente Triple Alliance Russian Empire Britain German Empire Austro-Hungarian Empire France Italy 1 August 1914 Serbia Germany as an ally of Austria declares war on Russia on 1 August 1914.

Combatants in the War Triple Entente Triple Alliance Russian Empire Britain German Empire Austro-Hungarian Empire France Italy 2 August 1914 Serbia Italy declares its neutrality, believing it is only required to support her allies if they are attacked but not if they are the aggressors.

Combatants in the War Triple Entente Triple Alliance Russian Empire Britain German Empire France Austro-Hungarian Empire Serbia 3 August 1914 Germany declares war on Russia‘s ally France. German troops advance into Belgium following the Schlieffen Plan.

Combatants in the War Triple Entente Triple Alliance Russian Empire Britain German Empire Belgium France Austro-Hungarian Empire Serbia 3 August 1914 Britain demands that German troops withdraw from neutral Belgium. Germany does not withdraw its troops and Britain declares war on Germany.

Combatants in the War Triple Entente Triple Alliance Russian Empire Britain German Empire Belgium France Austro-Hungarian Empire Serbia 4 August 1914 Germany declares war on Belgium.

Combatants in the War Triple Entente Triple Alliance Russian Empire Britain German Empire Belgium France Austro-Hungarian Empire Serbia 4 August 1914 Belgium enters the war.

Combatants in the War Triple Entente Triple Alliance Russian Empire Britain German Empire Belgium France Austro-Hungarian Empire Serbia Montenegro 5 August 1914 Montenegro declares war on Austria in support of Serbia and 3 days later declares war on Germany.

Combatants in the War Triple Entente Triple Alliance Russian Empire Britain German Empire Belgium France Austro-Hungarian Empire Serbia Montenegro 6 August 1914 Serbia declares war on Germany.

Combatants in the War Triple Entente Triple Alliance Russian Empire Britain German Empire Belgium France Austro-Hungarian Empire Serbia Montenegro 6 August 1914 Austria-Hungary declares war on Russia.

Combatants in the War Triple Entente Triple Alliance Russian Empire Britain German Empire Belgium France Austro-Hungarian Empire Serbia Montenegro 12 August 1914 Britain declares war on Austria-Hungary.

Combatants in the War Triple Entente Triple Alliance Russian Empire Britain German Empire Belgium France Austro-Hungarian Empire Serbia Montenegro 12 August 1914 France declares war on Austria-Hungary.

Combatants in the War Triple Entente Triple Alliance Russian Empire Britain German Empire Belgium France Austro-Hungarian Empire Serbia Montenegro 23 August 1914 Japan declares war on Germany.

Combatants in the War Triple Entente Triple Alliance Russian Empire Britain German Empire Belgium France Austro-Hungarian Empire Serbia Montenegro 25 August 1914 Japan declares war on Austria-Hungary.

Combatants in the War Triple Entente Triple Alliance Russian Empire Britain German Empire Belgium France Austro-Hungarian Empire Serbia Montenegro 28 August 1914 Austria-Hungary declares war on Belgium.

Combatants in the War Triple Entente Triple Alliance Russian Empire Britain German Empire Belgium France Austro-Hungarian Empire Serbia Montenegro Ottoman Empire 29 August 1914 The Ottoman Empire enters the war on the side of the Central Powers.

Combatants in the War Triple Entente Triple Alliance Russian Empire Britain German Empire Belgium France Austro-Hungarian Empire Serbia Montenegro Ottoman Empire 2 November 1914 Russia declares war on the Ottoman Empire.

Combatants in the War Triple Entente Triple Alliance Russian Empire Britain German Empire Belgium France Austro-Hungarian Empire Serbia Montenegro Ottoman Empire 2 November 1914 Serbia declares war on the Ottoman Empire.

Combatants in the War Triple Entente Triple Alliance Russian Empire Britain German Empire Belgium France Austro-Hungarian Empire Serbia Montenegro Ottoman Empire 5 November 1914 Britain declares war on the Ottoman Empire.

Combatants in the War Triple Entente Triple Alliance Russian Empire Britain German Empire Belgium France Austro-Hungarian Empire Serbia Montenegro Ottoman Empire 5 November 1914 France declares war on the Ottoman Empire.

Combatants in the War Triple Entente Triple Alliance Russian Empire Britain German Empire Belgium Austro-Hungarian Empire France Italy Serbia Montenegro Ottoman Empire 23 May 1915 Italy enters the war on the side of the Entente Powers instead of its former allies, the Central Powers.

Combatants in the War Triple Entente Triple Alliance Russian Empire Britain German Empire Belgium Austro-Hungarian Empire France Italy Serbia Montenegro Ottoman Empire 3 June 1915 San Marino declares war on Austria-Hungary.

Combatants in the War Triple Entente Triple Alliance Russian Empire Britain German Empire Belgium Austro-Hungarian Empire France Italy Serbia Montenegro Ottoman Empire 21 August 1915 Italy declares war on the Ottoman Empire.

Combatants in the War Triple Entente Triple Alliance Russian Empire Britain German Empire Belgium Austro-Hungarian Empire France Italy Serbia Montenegro Ottoman Empire 28 August 1915 Italy declares war on Germany.

Combatants in the War Triple Entente Triple Alliance Russian Empire Britain German Empire Belgium Austro-Hungarian Empire France Italy Serbia Montenegro Bulgaria Ottoman Empire 14 October 1915 Bulgaria declares war on Serbia.

Combatants in the War Triple Entente Triple Alliance Russian Empire Britain German Empire Belgium Austro-Hungarian Empire France Italy Serbia Montenegro Bulgaria Ottoman Empire 15 October 1915 Britain declares war on Bulgaria.

Combatants in the War Triple Entente Triple Alliance Russian Empire Britain German Empire Belgium Austro-Hungarian Empire France Italy Serbia Montenegro Bulgaria Ottoman Empire 15 October 1915 France declares war on Bulgaria.

Combatants in the War Triple Entente Triple Alliance Russian Empire Britain German Empire Belgium Austro-Hungarian Empire France Italy Serbia Montenegro Bulgaria Ottoman Empire 15 October 1915 Montenegro declares war on Bulgaria.

Combatants in the War Triple Entente Triple Alliance Russian Empire Britain German Empire Belgium Austro-Hungarian Empire France Italy Serbia Montenegro Bulgaria Ottoman Empire 19 October 1915 Italy declares war on Bulgaria.

Combatants in the War Triple Entente Triple Alliance Russian Empire Britain German Empire Belgium Austro-Hungarian Empire France Italy Serbia Montenegro Bulgaria Ottoman Empire 19 October 1915 Russia declares war on Bulgaria.

Combatants in the War Triple Entente Triple Alliance Russian Empire Britain German Empire Belgium Austro-Hungarian Empire France Italy Serbia Montenegro Bulgaria Ottoman Empire 9 March 1916 Germany declares war on Portugal.

Combatants in the War Triple Entente Triple Alliance Russian Empire Britain German Empire Belgium Austro-Hungarian Empire France Italy Serbia Montenegro Portugal 9 March 1916 Bulgaria Ottoman Empire Portugal declares war on the Central Powers.

Combatants in the War Triple Entente Triple Alliance Russian Empire Britain German Empire Belgium Austro-Hungarian Empire France Italy Serbia Montenegro Portugal 27 May 1916 Romania Bulgaria Ottoman Empire Romania declares war on Austria-Hungary.

Combatants in the War Triple Entente Triple Alliance Russian Empire Britain German Empire Belgium Austro-Hungarian Empire France Italy Serbia Montenegro Romania Bulgaria Portugal 1 September 1916 Ottoman Empire Bulgaria declares war on Romania.

Japan, as an ally of Britain, had declared war on Germany and Austria-Hungary on 23 -25 August 1914. Canada Japan India Combatants in the War Triple Entente Triple Alliance South Africa Globally the European Empires are able to draw on the military support of their colonies and dominions. The British Dominions: Australia, Canada, India, South Africa and New Zealand declare war against Germany and Austria-Hungary on 4 August 1914. Britain and France are also able to call on the troops of their colonies in Africa and Asia and so did Germany. Australia New Zealand

USA Canada USA Japan India Combatants in the War Triple Entente Triple Alliance South Africa Australia New Zealand 6 April 1917 The United States of America (USA) enters the war on the side of the Entente Powers (Allies)

USA Canada USA Japan India Panama Combatants in the War Triple Entente Triple Alliance Australia South Africa New Zealand 7 April 1917 Panama declares war on Germany.

USA Canada USA Japan Cuba India Panama Combatants in the War Triple Entente Triple Alliance South Africa Australia New Zealand 7 April 1917 Cuba declares war on Germany.

USA Canada USA Greece Japan Cuba India Panama Combatants in the War Triple Entente Triple Alliance South Africa Australia New Zealand 27 June 1917 Greece declares war on the Central Powers.

USA Canada USA Japan Cuba India Siam Panama Combatants in the War Triple Entente Triple Alliance South Africa Australia New Zealand 22 July 1917 Siam, now known as Thailand, enters the war on the side of Britain and France, the two major powers in Indo-China at that time, in the hope of securing its independence after the war.

USA Canada USA Japan Cuba India Siam Panama Combatants in the War Triple Entente Liberia South Africa Australia Triple Alliance New Zealand 4 August 1917 Liberia declares war on the Central Powers

USA Canada USA China Cuba Japan India Siam Panama Liberia Combatants in the War Triple Entente Triple Alliance South Africa Australia New Zealand 14 August 1918 Having been neutral for the first four years of the war, China declares war on the Central Powers to increase its chances of gaining control of the Shantung peninsula after the war.

USA Canada USA China Cuba Japan India Siam Panama Liberia Brazil Combatants in the War Triple Entente Triple Alliance South Africa Australia New Zealand 26 October 1917 Brazil declares war on Germany.

USA Canada USA China Cuba Japan India Siam Liberia Panama Brazil Combatants in the War Triple Entente Triple Alliance South Africa Australia New Zealand 10 December 1917 Panama declares war on Austria-Hungary.

USA Canada USA China Cuba India Siam Guatemala Liberia Panama Combatants in the War Triple Entente Triple Alliance Japan Brazil South Africa Australia New Zealand 23 April 1918 Guatemala declares war on the Central Powers.

USA Canada USA China Cuba Japan India Guatemala Nicaragua Panama Siam Liberia Brazil Combatants in the War Triple Entente Triple Alliance South Africa Australia New Zealand 8 May 1918 Nicaragua declares war on the Central Powers.

USA Canada USA China Cuba Japan India Siam Guatemala Nicaragua Costa Rica Panama Liberia Brazil Combatants in the War Triple Entente Triple Alliance South Africa Australia New Zealand 23 May 1918 Costa Rica declares war on the Central Powers.

USA Canada USA China Cuba Haiti Nicaragua Guatemala Costa Rica Panama Japan India Siam Liberia Brazil Combatants in the War Triple Entente Triple Alliance Australia South Africa New Zealand 12 July 1918 Haiti declares war on the Central Powers.

USA Canada USA China Cuba Haiti Guatemala Honduras Costa Rica Nicaragua Panama Japan India Siam Liberia Brazil Combatants in the War Triple Entente Triple Alliance South Africa Australia New Zealand 19 July 1918 Honduras declares war on the Central Powers.