Participants in World War I

Map of the World showing the participants in World War I. Those fighting on the side of the Triple Entente (at one point or another) are depicted in green, the Central Powers in orange, and neutral countries in grey.

This is a list of countries that participated in World War I, sorted by alphabetical order.

The Entente Forces

Note: The Entente Forces are sometimes also referred to as the Entente Powers or Allies of World War I.

• Andorra
• Belgium
• Brazil
• China
• Costa Rica
• Cuba
• Czechoslovak Legions
• France
• Greece
• Guatemala
• Haiti
• Honduras
• Italy
• Japan
• Liberia
• Montenegro
• Nepal
• Nicaragua
• Panama
• Portugal
• Romania
• Russia
  • Russian SFSR until Treaty of Brest-Litovsk
• San Marino
• Serbia
• Siam (now Thailand)
• United Kingdom
  • Australia
  • Canada
  • India (now India, Bangladesh, Burma and Pakistan)
  • Newfoundland
  • New Zealand
  • South Africa
  • British crown colonies
• United States
  • Alaska
  • Hawaii
  • Philippines
  • Puerto Rico
  • Other unincorporated territories

The Central Powers

• Austria-Hungary (now Austria, Bosnia and Herzegovina, Croatia, Czech Republic, Hungary, parts of northeast Italy, partially Poland, Romania, Slovakia, Slovenia,and Ukraine)
• Bulgaria (now Bulgaria, partially Greece, partially Republic of Macedonia)
• Germany (at the time the empire occupied Burundi, Cameroon, small parts of People's Republic of China, partially Gabon, Germany, Ghana, Marshall Islands, Federated States of Micronesia, Namibia, northeastern Nigeria, Palau, northern Papua New Guinea, partially Poland, Republic of the Congo, Rwanda, Samoa, mainland Tanzania, and Togo)
• Ottoman Empire (now Iraq, Israel, Jordan, Lebanon, partially Saudi Arabia, Syria, most of Turkey)

Neutral states

• Afghanistan - received a German diplomatic mission trying to convince it to act against the British in India
• Argentina
• Belgium
• Bolivia
• Bhutan
• Chile
• Colombia
• Denmark - Traded with both sides.
• El Salvador
• Ethiopia - received a German diplomatic mission trying to convince it to act against the British in Africa
• Liechtenstein - Had a customs and monetary union with Austria-Hungary.
• Luxembourg - Never declared war on the Central Powers despite being invaded and occupied by Germany.
• Mexico - Declined an alliance with Germany (see Zimmermann Telegram).
• Netherlands - An ally of the United Kingdom by treaty. Traded with both sides.
• Norway - Gave naval assistance to the United Kingdom.
• Paraguay
• Persia - Occupied by British and Russian troops.
• Spain - Also treaty bound ally to the United Kingdom.
• Sweden - Financially supported Germany.
• Switzerland - Switzerland did declare a "state of siege".
• Venezuela - Supplied the Allies with oil.

Declarations of War

European military alliances prior to the war.

Allies and Central Powers, early August 1914.

Allies and Central Powers, mid 1918.

The following table shows the timeline of the several declarations of war among the belligerent powers. Entries on a yellow background show severed diplomatic relations only, not actual declarations of war.

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

Notes

1. ^ The British Empire was the common term for the United Kingdom and its overseas possessions at this time. The term refers to the colonies it controlled, to the Indian Empire, which, while not officially designated a colony, was functionally indistinguishable from one, and the British Dominions - former colonies which were self-governing in most respects but whose foreign policy was controlled by London; Australia, Canada, Newfoundland, New Zealand and South Africa. At that time, the United Kingdom of Great Britain and Ireland also included the entire island of Ireland.

See also

• Participants in World War II
• Allies of World War I
• Triple Entente
• Triple Alliance
• Central Powers