Allied Powers

World War One technically began as a strictly European conflict with Austria-Hungary's declaration of war against the Kingdom of Serbia on July 28th, 1914. Within literally days it escalated as Russia initiated mobilization of its army and reservists as a precautionary measure, and in sympathy with its Serbian Slavic "cousins". Refusing Germany's ultimatum to stand down its mobilization, which had not yet taken any offensive action against any state, Germany subsequently declared war upon the Russian Empire on August 1st.

This brought France into war against Germany on August 3rd, and this development along with Germany's unprovoked invasion of neutral Belgium that same day, caused Great Britain to declare war against Germany on August 4th. These first three "Allied Powers", the empires of Russia, France and Britain, were known as the "Triple Entente", this name deriving from the "Entente Cordiale" agreement between Great Britain and France. The Entente Cordiale was the public and popular name for the Anglo-French agreement of 1904 and it was the basis for Great Britain's entry into the war on behalf of France and Russia, a true military mutual assistance treaty existing between  the latter two countries. Of course, Great Britain's entry also brought the "British Dominion" nations of Canada, Australia, New Zealand and South Africa into the war against Germany and Austria-Hungary. Japan's entry into the war, British and South African moves against Germany's African colonies, and Canadian, Australian and New Zealand contribution of troops to Britain's European war  theaters were what converted a European conflict into a "world war". 

The German propagandists were the first to use the term "Weltkrieg"  (world war), and it was soon picked up by both sides. The nations opposing the Germanic Empires quickly became simply and universally known as "The Allied Powers".
By the end of World War One in November 1918, some 26 countries had joined the Allied Powers and declared war upon the Central Powers. Presented below is a summary of the growing list of Allied Powers, ordered by  the year  they  formally entered  the war.

"Kriegserklärungen"
(declarations of war)
Publ. Essig - Basel (CH)

1914

    1915

1916

1917

1918

Serbia
Russia
France
Belgium
Japan
Montenegro
Great Britain
(Australia
New Zealand
Canada
South Africa)

Italy

Portugal
Romania

USA
Cuba
Brazil
Panama
Thailand
Liberia
China

Greece
Guatemala
Nicaragua
Costa Rica
Haiti

As well as those Latin American countries which formally declared war against Germany, most of the remainder severed diplomatic and economic relations with Germany and Austria-Hungary by early 1918. The motivations for Latin America turning against Germany were to protest that country's unhindered submarine warfare practices and as a show of solidarity with the United States. Significantly, America's immediate southern neighbour, Mexico, did not join in the war.

 

"Der Weltkrieg"
Publ. Essig-Basel (CH)

The major brunt of the war effort on the Allied side was borne by France, Great Britain and her four Dominion nations, Russia, Serbia and Belgium. These five nations alone of the twenty-six Allies accounted for over 91% of the 16.2 million Allied military casualties. While fifteen more nations joined the Allied cause during the course of the war, the only two additions that had substantive military impact on the ultimate Allied victory were the entry of the Kingdom of Italy in May 1915 and the United States in April 1917.