By 1914, it had transformed itself into a modern industrial state, with a powerful military; by defeating China in the First Sino-Japanese War during 1894-1895, it established itself as the primary power in East Asia and colonised the then-unified Korea and Formosa, now modern Taiwan. Concerned by Russian expansion in Korea and Manchuria, Britain and Japan signed the Anglo-Japanese Alliance on 30 January 1902, agreeing if either were attacked by a third party, the other would remain neutral and if attacked by two or more opponents, the other would come to its aid.

Arguments over whether to accept led to the National Schism, with an Entente-backed administration under Venizelos in Crete, and a Royalist one led by Constantine in Athens that supported the Central Powers. 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. A new national government under Venizelos joined the Entente, while the Greek National Defence Army Corps fought with the Allies on the Macedonian front. 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.

Harries & Harries 1991, p. United States. War Dept. General Staff. Ellis, John and Mike Cox. Pope, Stephen and Wheal, Elizabeth-Anne, eds. Tucker Spencer C (1999). The European Powers in the First World War: An Encyclopedia. War Office Statistics 2006, p. War Office Statistics 2006, p. Higham, Robin and Dennis E. Showalter, eds. Gilbert, Martin (1995). First World War. Wars and Population. Honolulu: University Press of the Pacific. War Office Statistics 2006, p. Statistics of the Military Effort of the British Empire During the Great War 1914-1920. Uckfield, East Sussex: Military and Naval Press.

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.