World War One: Declarations of War

World War One officially began on July 28, 1914..

28 July 1914 Austria-Hungary declared war on Serbia

World War One officially ended on November 11, 1918

All Declarations of War by Date Order:

• 28 July 1914 Austria-Hungary declared war on Serbia
• 1 August 1914 Germany declared war on Russia
• 3 August 1914 Germany declared war on France
• 4 August 1914 Germany declared war on Belgium
• 4 August 1914 United Kingdom declared war on Germany
• 5 August 1914 Montenegro declared war on Austria-Hungary
• 6 August 1914 Austria-Hungary declared war on Russia
• 6 August 1914 Serbia declared war on Germany
• 9 August 1914 Montenegro declared war on Germany
• 11 August 1914 France declared war on Austria-Hungary
• 12 August 1914 United Kingdom declared war on Austria-Hungary
• 22 August 1914 Austria-Hungary declared war on Belgium
• 23 August 1914 Japan declared war on Germany
• 25 August 1914 Japan declared war on Austria-Hungary
• 1 November 1914 Russia declared war on Ottoman Empire
• 2 November 1914 Serbia declared war on Ottoman Empire
• 3 November 1914 Montenegro declared war on Ottoman Empire
• 5 November 1914 United Kingdom declared war on Ottoman Empire
• 5 November 1914 France declared war on Ottoman Empire
• 23 May 1915 Italy declared war on Austria-Hungary
• 3 June 1915 San Marino declared war on Austria-Hungary
• 21 August 1915 Italy declared war on Ottoman Empire
• 14 October 1915 Bulgaria declared war on Serbia
• 15 October 1915 United Kingdom declared war on Bulgaria
• 15 October 1915 Montenegro declared war on Bulgaria
• 16 October 1915 France declared war on Bulgaria
• 19 October 1915 Italy declared war on Bulgaria
• 19 October 1915 Russia declared war on Bulgaria
• 9 March 1916 Germany declared war on Portugal
• 15 March 1916 Austria-Hungary declared war on Portugal
• 27 August 1916 Romania declared war on Austria-Hungary
• 27 August 1916 Italy declared war on Germany
• 28 August 1916 Germany declared war on Romania
• 30 August 1916 Ottoman Empire declared war on Romania
• 1 November 1916 Bulgaria declared war on Romania
• 6 April 1917 United States declared war on Germany
• 7 April 1917 Cuba declared war on Germany
• 10 April 1917 Bulgaria declared war on United States
• 13 April 1917 Bolivia declared war on Germany
• 20 April 1917 Ottoman Empire declared war on United States
• 2 July 1917 Greece declared war on Germany
• 2 July 1917 Greece declared war on Austria-Hungary
• 2 July 1917 Greece declared war on Ottoman Empire
• 2 July 1917 Greece declared war on Bulgaria
• 22 July 1917 Siam declared war on Germany
• 22 July 1917 Siam declared war on Austria-Hungary
• 4 August 1917 Liberia declared war on Germany
• 14 August 1917 China declared war on Germany
• 14 August 1917 China declared war on Austria-Hungary
• 6 October 1917 Peru declared war on Germany
• 7 October 1917 Uruguay declared war on Germany
• 26 October 1917 Brazil declared war on Germany
• 7 December 1917 United States declared war on Austria-Hungary
• 7 December 1917 Ecuador declared war on Germany
• 10 December 1917 Panama declared war on Austria-Hungary
• 16 December 1917 Cuba declared war on Austria-Hungary
• 23 April 1918 Guatemala declared war on Germany
• 8 May 1918 Nicaragua declared war on Germany
• 8 May 1918 Nicaragua declared war on Austria-Hungary
• 23 May 1918 Costa Rica declared war on Germany
• 12 July 1918 Haiti declared war on Germany
• 19 July 1918 Honduras declared war on Germany
• 10 November 1918 Romania declared war on Germany

The Central Powers declarations of war during World War One were:

In Date Order

German Declarations of War

• 1 August 1914  Germany declared war on  Russia
• 3 August 1914  Germany declared war on  France
• 4 August 1914  Germany declared war on  Belgium
• 9 March 1916  Germany declared war on  Portugal
• 28 August 1916  Germany declared war on  Romania

Austria-Hungary Declarations of War

• 28 July 1914  Austria-Hungary declared war on  Serbia
• 6 August 1914  Austria-Hungary declared war on  Russia
• 22 August 1914  Austria-Hungary declared war on  Belgium
• 15 March 1916  Austria-Hungary declared war on  Portugal

Bulgarian Declarations of War

• 14 October 1915  Bulgaria declared war on  Serbia
• 1 November 1916  Bulgaria declared war on  Romania
• 10 April 1917  Bulgaria declared war on  United States

Ottoman Empire Declarations of War

• 30 August 1916  Ottoman Empire declared war on  Romania
• 20 April 1917  Ottoman Empire declared war on  United States

The Allied Forces declarations of war during World War One were:

• 4 August 1914  United Kingdom declared war on  Germany
• 5 August 1914  Montenegro declared war on  Austria-Hungary
• 6 August 1914  Serbia declared war on  Germany
• 9 August 1914  Montenegro declared war on  Germany
• 11 August 1914  France declared war on  Austria-Hungary
• 12 August 1914  United Kingdom declared war on  Austria-Hungary
• 23 August 1914  Japan declared war on  Germany
• 25 August 1914  Japan declared war on  Austria-Hungary
• 1 November 1914  Russia declared war on  Ottoman Empire
• 2 November 1914  Serbia declared war on  Ottoman Empire
• 3 November 1914  Montenegro declared war on  Ottoman Empire
• 5 November 1914  United Kingdom declared war on  Ottoman Empire
• 5 November 1914  France declared war on  Ottoman Empire
• 23 May 1915  Italy declared war on  Austria-Hungary
• 3 June 1915  San Marino declared war on  Austria-Hungary
• 21 August 1915  Italy declared war on  Ottoman Empire
• 15 October 1915  United Kingdom declared war on  Bulgaria
• 15 October 1915  Montenegro declared war on  Bulgaria
• 16 October 1915  France declared war on  Bulgaria
• 19 October 1915  Italy declared war on  Bulgaria
• 19 October 1915  Russia declared war on  Bulgaria
• 27 August 1916  Romania declared war on  Austria-Hungary
• 27 August 1916  Italy declared war on  Germany
• 6 April 1917  United States declared war on  Germany
• 7 April 1917  Cuba declared war on  Germany
• 13 April 1917  Bolivia declared war on  Germany
• 2 July 1917  Greece declared war on  Germany
• 2 July 1917  Greece declared war on  Austria-Hungary
• 2 July 1917  Greece declared war on  Ottoman Empire
• 2 July 1917  Greece declared war on  Bulgaria
• 22 July 1917  Siam declared war on  Germany
• 22 July 1917  Siam declared war on  Austria-Hungary
• 4 August 1917  Liberia declared war on  Germany
• 14 August 1917  China declared war on  Germany
• 14 August 1917  China declared war on  Austria-Hungary
• 6 October 1917  Peru declared war on  Germany
• 7 October 1917  Uruguay declared war on  Germany
• 26 October 1917  Brazil declared war on  Germany
• 7 December 1917  United States declared war on  Austria-Hungary
• 7 December 1917  Ecuador declared war on  Germany
• 10 December 1917  Panama declared war on  Austria-Hungary
• 16 December 1917  Cuba declared war on  Austria-Hungary
• 23 April 1918  Guatemala declared war on  Germany
• 8 May 1918  Nicaragua declared war on  Germany
• 8 May 1918  Nicaragua declared war on  Austria-Hungary
• 23 May 1918  Costa Rica declared war on  Germany
• 12 July 1918  Haiti declared war on  Germany
• 19 July 1918  Honduras declared war on  Germany
• 10 November 1918  Romania declared war on  Germany

Declarations of War By Country Order:

Against Germany

• 4 August 1914  United Kingdom declared war on  Germany
• 6 August 1914  Serbia declared war on  Germany
• 9 August 1914  Montenegro declared war on  Germany
• 23 August 1914  Japan declared war on  Germany
• 27 August 1916  Italy declared war on  Germany
• 6 April 1917  United States declared war on  Germany
• 7 April 1917  Cuba declared war on  Germany
• 13 April 1917  Bolivia declared war on  Germany
• 2 July 1917  Greece declared war on  Germany
• 22 July 1917  Siam declared war on  Germany
• 4 August 1917  Liberia declared war on  Germany
• 14 August 1917  China declared war on  Germany
• 6 October 1917  Peru declared war on  Germany
• 7 October 1917  Uruguay declared war on  Germany
• 26 October 1917  Brazil declared war on  Germany
• 7 December 1917  Ecuador declared war on  Germany
• 23 April 1918  Guatemala declared war on  Germany
• 8 May 1918  Nicaragua declared war on  Germany
• 23 May 1918  Costa Rica declared war on  Germany
• 12 July 1918  Haiti declared war on  Germany
• 19 July 1918  Honduras declared war on  Germany
• 10 November 1918  Romania declared war on  Germany

Against Austria-Hungary

• 5 August 1914  Montenegro declared war on  Austria-Hungary
• 11 August 1914  France declared war on  Austria-Hungary
• 12 August 1914  United Kingdom declared war on  Austria-Hungary
• 25 August 1914  Japan declared war on  Austria-Hungary
• 23 May 1915  Italy declared war on  Austria-Hungary
• 3 June 1915  San Marino declared war on  Austria-Hungary
• 27 August 1916  Romania declared war on  Austria-Hungary
• 2 July 1917  Greece declared war on  Austria-Hungary
• 22 July 1917  Siam declared war on  Austria-Hungary
• 14 August 1917  China declared war on  Austria-Hungary
• 7 December 1917  United States declared war on  Austria-Hungary
• 10 December 1917  Panama declared war on  Austria-Hungary
• 16 December 1917  Cuba declared war on  Austria-Hungary
• 8 May 1918  Nicaragua declared war on  Austria-Hungary

Against Ottoman Empire

• 1 November 1914  Russia declared war on  Ottoman Empire
• 2 November 1914  Serbia declared war on  Ottoman Empire
• 3 November 1914  Montenegro declared war on  Ottoman Empire
• 5 November 1914  United Kingdom declared war on  Ottoman Empire
• 5 November 1914  France declared war on  Ottoman Empire
• 21 August 1915  Italy declared war on  Ottoman Empire
• 2 July 1917  Greece declared war on  Ottoman Empire

Against Bulgaria

• 15 October 1915  United Kingdom declared war on  Bulgaria
• 15 October 1915  Montenegro declared war on  Bulgaria
• 16 October 1915  France declared war on  Bulgaria
• 19 October 1915  Italy declared war on  Bulgaria
• 19 October 1915  Russia declared war on  Bulgaria
• 2 July 1917  Greece declared war on  Bulgaria