[4] Archduke Franz Ferdinand of Austria, heir presumptive to the Austro-Hungarian throne, and his wife, Sophie, Duchess of Hohenberg, were assassinated on 28 June 1914 by Bosnian Serb student Gavrilo Princip.

[5] This provoked Austria to deliver an ultimatum to Serbia, listing ten demands made intentionally unacceptable to provide an excuse for starting hostilities.

[9] On 29 October 1914, the Ottoman Empire entered the war by launching a naval raid on Russian ports.

[16] Germany, facing a two-front war, enacted what was known as the Schlieffen Plan, which involved German armed forces moving through Belgium and swinging south into France and towards the French capital of Paris.

This plan was hoped to quickly gain victory against the French and allow German forces to concentrate on the Eastern Front.

This caused Great Britain to declare war against the German Empire, as the action violated the Treaty of London that both nations signed in 1839 guaranteeing Belgian neutrality.

Colonization was opposed by much of the government, including chancellor Otto von Bismarck, but it became a colonial power after participating in the Berlin Conference.

[25] German East Africa was founded in 1885 and expanded to include modern-day Tanzania (except Zanzibar), Rwanda, Burundi, and parts of Mozambique.

It was the only German colony to not be fully conquered during the war, with resistance by commander Paul von Lettow-Vorbeck lasting until November 1918.

Later it was surrendered to the Allies in 1919 and split between the Belgian Congo, Portuguese Mozambique, and the newly founded colony of Tanganyika.

The Ottoman Empire had gained strong economic connections with Germany through the Berlin-to-Baghdad railway project that was still incomplete at the time.

[43]: 292  However, for the first several months of the war, the Ottoman Empire maintained neutrality though it allowed a German naval squadron to enter and stay near the strait of Bosphorus.

[43]: 292 After pressure escalated from the German government demanding that the Ottoman Empire fulfill its treaty obligations, or else Germany would expel the country from the alliance and terminate economic and military assistance, the Ottoman government entered the war with the recently acquired cruisers from Germany, along with their own navy, launching a naval raid on the Russian ports of Odessa, Sevastopol, Novorossiysk, Feodosia, and Yalta,[10][11] thus engaging in military action in accordance with its alliance obligations with Germany.

[43]: 293 After Bulgaria's defeat in July 1913 at the hands of Serbia, Greece and Romania, it signed a treaty of defensive alliance with the Ottoman Empire on 19 August 1914.

[45] Bulgaria was the last country to join the Central Powers, which it did in October 1915 by declaring war on Serbia.

[47] As a condition of entering the war on the side of the Central Powers, Bulgaria was granted the right to reclaim that territory.

The Central Powers (mainly the Germans) began to attempt to incite unrest to hopefully divert French resources from Europe.

[57] During World War I, the Dervish State received many supplies from the German and Ottoman Empires to carry on fighting the Allies.

The Ethiopian Empire was officially neutral throughout World War I but widely suspected of sympathy for the Central Powers between 1915 and 1916.

Its ruler, Lij Iyasu, was widely suspected of harbouring pro-Islamic sentiments and being sympathetic to the Ottoman Empire.

One of the unsuccessful expeditions was led by Leo Frobenius, a celebrated ethnographer and personal friend of Kaiser Wilhelm II.

Under Iyasu's directions, Ethiopia probably supplied weapons to the Muslim Dervish rebels during the Somaliland Campaign of 1915 to 1916, indirectly helping the Central Powers' cause.

[76] Liechtenstein was officially neutral throughout World War I, though the general population and government was supportive of the Central Powers, particularly Austria-Hungary, of which the two countries had been in a customs union since 1852.

However, from September 1914 food deliveries from Austria-Hungary began to decrease, which quickly soured the initial war support.

[84] Following their armistice with the Central Powers, Romania was involved in the Russian Civil War against both the Whites and the Reds.

[86] Other movements supported the efforts of the Central Powers for their own reasons, such as the radical Irish Nationalists who launched the Easter Rising in Dublin in April 1916; they referred to their "gallant allies in Europe".

Piłsudski wanted his legions to help the Central Powers defeat Russia and then side with France and the UK and win the war with them.

[94] Austria and Hungary concluded ceasefires separately during the first week of November following the disintegration of the Habsburg Empire and the Italian offensive at Vittorio Veneto;[95][96] Germany signed the armistice ending the war on the morning of 11 November 1918 after the Hundred Days Offensive, and a succession of advances by New Zealand, Australian, Canadian, Belgian, British, French and US forces in north-eastern France and Belgium.