The Allies or the Entente (UK: , US: on-TONT) was an international military coalition of countries led by the French Republic, the United Kingdom, the Russian Empire, the United States, the Kingdom of Italy, and the Empire of Japan against the Central Powers of the German Empire, Austria-Hungary, the Ottoman Empire, and the Tsardom of Bulgaria in World War I (1914–1918).
By the end of the first decade of the 20th century, the major European powers were divided between the Triple Entente and the Triple Alliance. The Triple Entente was made up of the United Kingdom, France, and Russia. The Triple Alliance was originally composed of Germany, Austria–Hungary, and Italy, but Italy remained neutral in 1914. As the war progressed, each coalition added new members. Japan joined the Entente in 1914 and, despite proclaiming its neutrality at the beginning of the war, Italy also joined the Entente in 1915. The term "Allies" became more widely used than "Entente", although the United Kingdom, France, Russia, and Italy were also referred to as the Quadruple Entente and, together with Japan, as the Quintuple Entente. The five British Dominions (the Commonwealth of Australia, the Dominion of Canada, the Dominion of New Zealand, the Dominion of Newfoundland, and the Union of South Africa) all fought alongside the British. The colonies of Allied countries, such as the American Philippines, Belgian Congo, British India, French Algeria, and Japanese Korea, were also used as a source of manpower by the colonial powers.
The United States joined near the end of the war in 1917 (the same year in which Russia withdrew from the conflict) as an "associated power" rather than an official ally. Primary reasons for why the United States joined the war include the unrestricted submarine warfare waged by Germany in the Atlantic, the revelation of the Zimmermann telegram, and strong economic and political ties with the Allies. Other "associated members" of the Allies included Serbia, Belgium, Montenegro, Asir, Nejd and Hasa, Portugal, Romania, Hejaz, Panama, Cuba, Greece, China, Siam, Brazil, Armenia, Luxembourg, Guatemala, Nicaragua, Costa Rica, Haiti, Liberia, and Honduras. The treaties signed at the Paris Peace Conference recognised the British Empire, France, Italy, Japan, and the United States as "the Principal Allied and Associated Powers"; France, the UK, Italy, and the US were also referred as the "Big Four" top powers of the war.
When the war began in 1914, the Central Powers were opposed by the Triple Entente, formed in 1907 when the agreement between the United Kingdom and Russia complemented existing agreements between the three powers.
Fighting commenced when Austria invaded Serbia on 28 July 1914, in response to the assassination of Archduke Franz Ferdinand, heir to Emperor Franz Joseph I; this brought Serbia's ally Montenegro into the war on 9 August and it attacked the Austrian naval base at Cattaro, modern Kotor. At the same time, German troops carried out the Schlieffen Plan, entering neutral Belgium and Luxembourg; over 95% of Belgium was occupied but the Belgian Army held their lines on the Yser Front throughout the war. This allowed Belgium to be treated as an Ally, in contrast to Luxembourg which retained control over domestic affairs but was occupied by the German military.
In the East, between 7 and 9 August the Russians entered German East Prussia and Austrian Eastern Galicia. Japan joined the Entente by declaring war on Germany on 23 August, then Austria on 25 August. On 2 September, Japanese forces surrounded the German Treaty Port of Tsingtao (now Qingdao) in China and occupied German colonies in the Pacific, including the Mariana, Caroline, and Marshall Islands.
Despite its membership of the Triple Alliance, Italy remained neutral until 23 May 1915 when it joined the Entente, declaring war on Austria but not Germany. On 17 January 1916, Montenegro capitulated and left the Entente; this was offset when Germany declared war on Portugal in March 1916, while Romania commenced hostilities against Austria on 27 August.
On 6 April 1917, the United States entered the war as a co-belligerent, along with the associated allies of Liberia, Siam and Greece. After the 1917 October Revolution, Russia left the Entente and agreed to a separate peace with the Central Powers with the signing of the Treaty of Brest-Litovsk on 3 March 1918. Romania was forced to do the same in the May 1918 Treaty of Bucharest but on 10 November, it repudiated the Treaty and once more declared war on the Central Powers.
These changes meant the Allies who negotiated the Treaty of Versailles in 1919 included the United Kingdom, France, Italy, Japan and the United States; Part One of the Treaty agreed to the establishment of the League of Nations on 25 January 1919. This came into being on 16 January 1920 with Britain, France, Italy and Japan as permanent members of the Executive Council; the US Senate voted against ratification of the treaty on 19 March, thus preventing the United States from joining the League.
For similar statistics of the Central Powers, see Central Powers#Statistics.
For much of the 19th century, Britain sought to maintain the European balance of power without formal alliances, a policy known as splendid isolation. This left it dangerously exposed as Europe divided into opposing power blocs. In response, the 1895–1905 Conservative government negotiated first the 1902 Anglo-Japanese Alliance, then the 1904 Entente Cordiale with France. The first tangible result of this shift was British support for France against Germany in the 1905 Moroccan Crisis.
The 1905–1915 Liberal government continued this re-alignment with the 1907 Anglo-Russian Convention. Like the Anglo-Japanese and Entente agreements, it focused on settling colonial disputes but by doing so paved the way for wider co-operation and allowed Britain to refocus resources in response to German naval expansion.
Since control of Belgium allowed an opponent to threaten invasion or blockade British trade, preventing it was a long-standing British strategic interest. Under Article VII of the 1839 Treaty of London, Britain guaranteed Belgian neutrality against aggression by any other state, by force if required. Chancellor Theobald von Bethmann Hollweg later dismissed this as a 'scrap of paper,' but British law officers routinely confirmed it as a binding legal obligation and its importance was well understood by Germany.
The 1911 Agadir Crisis led to secret discussions between France and Britain in case of war with Germany. These agreed that within two weeks of its outbreak, a British Expeditionary Force of 100,000 men would be landed in France; in addition, the Royal Navy would be responsible for the North Sea, the Channel and protecting Northern France, with the French navy concentrated in the Mediterranean. Britain was committed to support France in a war against Germany but this was not widely understood outside government or the upper ranks of the military.
As late as 1 August, a clear majority of the Liberal government and its supporters wanted to stay out of the war. While Liberal leaders H. H. Asquith and Edward Grey considered Britain legally and morally committed to support France regardless, waiting until Germany triggered the 1839 Treaty provided the best chance of preserving Liberal party unity.
The German high command was aware entering Belgium would lead to British intervention but decided the risk was acceptable; they expected a short war while their ambassador in London claimed troubles in Ireland would prevent Britain from assisting France. On 3 August, Germany demanded unimpeded progress through any part of Belgium and when this was refused, invaded early on the morning of 4 August.
This changed the situation; the invasion of Belgium consolidated political and public support for the war by presenting what appeared to be a simple moral and strategic choice. The Belgians asked for assistance under the 1839 Treaty and in response, Britain declared war on Germany on 4 August 1914. Although Germany's violation of Belgium neutrality was not the only cause of British entry into the war, it was used extensively in government propaganda at home and abroad to make the case for British intervention. This confusion arguably persists today.