[1][2] The colonies administered by the countries that fought for the Allies were also part of the Entente powers such as American Philippines, Belgian Congo, British India, French Algeria, and Japanese Korea.

Other "associated members" 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.

On 17 January 1916, Montenegro capitulated and left the Entente;[7] this was offset when Germany declared war on Portugal in March 1916, while Romania commenced hostilities against Austria on 27 August.

[9] 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.

(inc. Congress Poland and Vistula Land) 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 and the 1895–1905 Conservative government negotiated first the 1902 Anglo-Japanese Alliance, then the 1904 Entente Cordiale with France.

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.

[25] 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.

[29] 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.

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.

While France took advantage of this to agree the 1894 Franco-Russian Alliance, Britain viewed Russia with deep suspicion; in 1800, over 3,000 kilometres separated the Russian Empire and British India, by 1902, it was 30 km in some areas.

In 1908, Austria annexed the former Ottoman province of Bosnia and Herzegovina; Russia responded by creating the Balkan League in order to prevent further Austrian expansion.

This resulted in the 1904 Entente Cordiale with Britain; like the 1907 Anglo-Russian Convention, for domestic British consumption it focused on settling colonial disputes but led to informal co-operation in other areas.

[46] Colonial troops also fought at Gallipoli, occupied Togo and Kamerun in West Africa and had a minor role in the Middle East, where France was the traditional protector of Christians in the Ottoman provinces of Syria, Palestine and Lebanon.

Italian nationalists referred to Austrian-held Istria (including Trieste and Fiume) and Trento as 'the lost territories', making the Alliance so controversial that the terms were kept secret until it expired in 1915.

[55] The Italian Prime Minister Antonio Salandra argued that as the Alliance was defensive in nature, Austria's aggression against Serbia and Italy's exclusion from the decision-making process meant it was not obliged to join them.

[38] Austria viewed Serbia with hostility partly due to its links with Russia, whose claim to be the protector of South Slavs extended to those within the Austro-Hungarian Empire, such as the Czechs and Slovaks.

Between 1914 and 1918, Serbia suffered the greatest proportional losses of any combatant, with over 25% of all those mobilised becoming casualties; including civilians and deaths from disease, over 1.2 million died, nearly 30% of the entire population.

Article VII of the Treaty required Belgium to remain perpetually neutral and committed Austria, France, Germany and Russia to guarantee that against aggression by any other state, including the signatories.

[43] While neither Britain or France could allow Germany to occupy Belgium unopposed, a Belgian refusal to ask for help would complicate matters for the British Liberal government, which contained a significant isolationist element.

The growth of the Russian railway network and increase in speed of mobilisation made rapid victory over France even more important; to accommodate the additional 170,000 troops approved by the 1913 Army Bill, the 'incursion' now became a full-scale invasion.

In 1908, the island of Crete, formally part of the Ottoman Empire but administered by Greek officials, declared union with Greece, led by the charismatic nationalist Eleftherios Venizelos.

A year later, young army officers formed the Military League to advocate for an aggressive and expansionist foreign policy; with their backing, Venizelos won a majority in the 1910 Parliamentary elections, followed by another in 1912.

In 1913, the Greek monarch George I was assassinated; he was succeeded by his son Constantine who had attended Heidelberg University, served in a Prussian regiment and married Sophia of Prussia, sister of Emperor William II.

[68] In September 1915, Bulgaria joined the Central Powers; in October, Venizelos allowed Entente forces to land at Thessaloniki or Salonica to support the Serbs, although they were too late to prevent their defeat.

In August 1916, Bulgarian troops advanced into Greek-held Macedonia and Constantine ordered the army not to resist; anger at this led to a coup and he was eventually forced into exile in June 1917.

[71] In addition to the lack of substantive gains from the Balkan Wars, there were long-running internal divisions between those who like Nicholas I preferred an independent Montenegro and those who advocated union with Serbia.

[87] Despite being relatively short, the Romanian campaign of 1916 provided considerable respite for the Western Allies, as the Germans ceased all their other offensive operations in order to deal with Romania.

In compliance with the commitments made at the Inter-American Conference, held in Paris from 20 November to 3 December 1917, the Brazilian Government sent a medical mission composed of civilian and military surgeons to work in field hospitals of the European theatre, a contingent of sergeants and officers to serve with the French Army; Airmen from the Army and Navy to join the Royal Air Force, and the employment of part of the Fleet, primarily in the anti-submarine war.

[92] The remotely connected Zimmermann Telegram of the same period, within which the Germans promised to help Mexico regain some of its territory lost to the US nearly seven decades before in the event of the United States entering the war, was also a contributing factor.