War Entry Dates, Central Powers and Allies

 

Against the Allies
  Entry End Years Months Days Total Combat
Austria-Hungary 28 July, 1914 4 November, 1918 4 3 8 1,561 Y
Germany 1 August, 1914 11 November, 1918 4 3 11 1,564 Y
Bulgaria 14 October, 1914 29 September, 1918 3 11 17 1,447 Y
Ottoman Empire 29 October, 1914 30 October, 1918 3 11 2 1,433 Y

 

Against the Central Powers
  Entry End Years Months Days Total Combat
Serbia 28 July, 1914 11 November, 1918 4 3 15 1,568 Y
Russia 1 August, 1914 3 March, 1918 3 7 3 1,311 Y
France 3 August, 1914 11 November, 1918 4 3 9 1,562 Y
Belgium 4 August, 1914 11 November, 1918 4 3 8 1,561 Y
United Kingdom 4 August, 1914 11 November, 1918 4 3 8 1,561 Y
Australia 4 August, 1914 11 November, 1918 4 3 8 1,561 Y
Canada 4 August, 1914 11 November, 1918 4 3 8 1,561 Y
New Zealand 4 August, 1914 11 November, 1918 4 3 8 1,561 Y
Montenegro 6 August, 1914 17 January, 1916 1 5 12 530 Y
Japan 23 August, 1914 11 November, 1918 4 2 20 1,542 Y
Portugal 23 November, 1914 11 November, 1918 3 11 20 1,450 Y
Italy 23 May, 1915 11 November, 1918 3 5 20 1,269 Y
San Marino 3 June, 1915 4 November, 1918 3 5 2 1,251 -
Romania 27 August, 1916 7 May, 1918 1 8 11 619 Y
United States 6 April, 1917 11 November, 1918 1 7 6 585 Y
Panama 7 April, 1917 11 November, 1918 1 7 5 584 -
Cuba 7 April, 1917 11 November, 1918 1 7 5 584 -
Greece 28 June, 1917 11 November, 1918 1 4 15 502 Y
Siam 22 July, 1917 11 November, 1918 1 3 21 478 -
Liberia 4 August, 1917 11 November, 1918 1 3 8 465 -
China 14 August, 1917 11 November, 1918 1 2 29 455 -
Brazil 26 October, 1917 11 November, 1918 1 0 17 382 -
Guatemala 21 April 1918 11 November, 1918 - 6 22 205 -
Nicaragua 6 May, 1918 11 November, 1918 - 6 6 190 -
Costa Rica 23 May, 1918 11 November, 1918 - 5 20 173 -
Haiti 12 July, 1918 11 November, 1918 - 4 0 123 -
Honduras 19 July, 1918 11 November, 1918 - 3 24 116 -

 

Notes:

(1) Total days count includes end date.

Source: Adapted from The War With Germany: A Statistical Survey.