World War One: Declarations of War

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

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