Participants in World War I
This is a list of countries that participated in World War I, sorted by alphabetical order.
The Entente Powers
Note: The "Entente Powers" are also known as the Allies of World War I or the Allies
- Arab Rebels
- Republic of China
- Costa Rica
- Czechoslovak Legions
- Emirate of Nejd and Hasa
- France (French colonial empire)
- New Hebrides (British-French condominium)
- Portugal (Portuguese colonial empire)
- Siam (now Thailand)
- United Kingdom (British Empire)
- United States
- Non Independent ethnic groups: Armenians, Assyrians, Poles, Pontic Greeks
The Central Powers
- Azerbaijan Democratic Republic
- Dervish State
- Jabal Shammar
- Ottoman Empire
- Sultanate of Darfur
- Ukrainian State
- Non Independent ethnic groups: Poles
- Afghanistan – received a German diplomatic mission trying to convince it to act against the British in India
- Principality of Albania – In political chaos since the beginning of the war, the country was occupied by both Central and Allied powers but never declared war on either side
- El Salvador
- Ethiopia – received a German diplomatic mission trying to convince it to act against Italy, United Kingdom and France in East 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
- Bogd Khaanate of Mongolia
- / 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.
- Persia – Civil dispute and Allied Campaign against Ottomans
- Spitsbergen – Danish-Norwegian co-dominium
- Sweden – Non-belligerent
- Switzerland – Switzerland did declare a "state of siege"
- Venezuela – Supplied the Allies with oil
Declarations of war
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.
- ^ 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.