The Central Powers, also known as the Central Empires, were one of the two main coalitions that fought in World War I (1914–1918). It consisted of the German Empire, Austria-Hungary, the Ottoman Empire, and Bulgaria; this was also known as the Quadruple Alliance.
The Triple Alliance was a defensive military alliance between Germany, Austria-Hungary, and Italy. It was formed on 20 May 1882 and renewed periodically until it expired in 1915 during World War I. Germany and Austria-Hungary had been closely allied since 1879. Italy was looking for support against France shortly after it lost North African ambitions to the French. Each member promised mutual support in the event of an attack by any other great power. The treaty provided that Germany and Austria-Hungary were to assist Italy if it was attacked by France without provocation. In turn, Italy would assist Germany if attacked by France. In the event of a war between Austria-Hungary and Russia, Italy promised to remain neutral.
The League of the Balkans was a quadruple alliance formed by a series of bilateral treaties concluded in 1912 between the Eastern Orthodox kingdoms of Greece, Bulgaria, Serbia and Montenegro, and directed against the Ottoman Empire, which at the time still controlled much of Southeastern Europe.
The aftermath of World War I saw far-reaching and wide-ranging cultural, economic, and social change across Europe, Asia, Africa, and even in areas outside those that were directly involved. Four empires collapsed due to the war, old countries were abolished, new ones were formed, boundaries were redrawn, international organizations were established, and many new and old ideologies took a firm hold in people's minds. Additionally, culture in the nations involved was greatly changed. World War I also had the effect of bringing political transformation to most of the principal parties involved in the conflict, transforming them into electoral democracies by bringing near-universal suffrage for the first time in history, as in Germany, Great Britain, and Turkey.
The Triple Entente describes the informal understanding between the Russian Empire, the French Third Republic, and the United Kingdom of Great Britain and Ireland. It was built upon the Franco-Russian Alliance of 1894, the Entente Cordiale of 1904 between France and Britain, and the Anglo-Russian Entente of 1907. It formed a powerful counterweight to the Triple Alliance of the German Empire, the Austro-Hungarian Empire, and the Kingdom of Italy. The Triple Entente, unlike the Triple Alliance or the Franco-Russian Alliance itself, was not an alliance of mutual defence.
The identification of the causes of World War I remains a debated issue. World War I began in the Balkans on July 28, 1914, and hostilities ended on November 11, 1918, leaving 17 million dead and 25 million wounded. Moreover, the Russian Civil War can in many ways be considered a continuation of World War I, as can various other conflicts in the direct aftermath of 1918.
The Allies, the Entente or the Triple Entente was an international military coalition of countries led by France, the United Kingdom, Russia, the United States, Italy, and Japan against the Central Powers of Germany, Austria-Hungary, the Ottoman Empire, and Bulgaria in World War I (1914–1918).
The Middle Eastern theatre of World War I saw action between 30 October 1914 and 30 October 1918. The combatants were, on one side, the Ottoman Empire, with some assistance from the other Central Powers; and on the other side, the British as well as troops from the British Dominions of Australia, Canada, and New Zealand, the Russians, and the French from among the Allied Powers. There were five main campaigns: the Sinai and Palestine, Mesopotamian, Caucasus, Persian, and Gallipoli campaigns.
Russo-Turkish wars or Russo-Ottoman wars were a series of twelve wars fought between the Russian Empire and the Ottoman Empire between the 16th and 20th centuries. It was one of the longest series of military conflicts in European history. Except for the war of 1710–11, as well as the Crimean War which is often treated as a separate event, the conflicts ended disastrously for the Ottoman Empire, which was undergoing a long period of stagnation and decline; conversely, they showcased the ascendancy of Russia as a European power after the modernization efforts of Peter the Great in the early 18th century.
The Balkans theatre or Balkan campaign was a theatre of World War I fought between the Central Powers and the Allies.
World War I or the First World War, also known as the Great War, was a global conflict between two coalitions: the Allies and the Central Powers. Fighting took place mainly in Europe and the Middle East, as well as in parts of Africa and the Asia-Pacific, and in Europe was characterised by trench warfare and the use of artillery, machine guns, and chemical weapons (gas). World War I was one of the deadliest conflicts in history, resulting in an estimated 9 million military dead and 23 million wounded, plus up to 8 million civilian deaths from causes including genocide. The movement of large numbers of troops and civilians was a major factor in spreading the Spanish flu pandemic, which killed millions.
The Kingdom of Romania was neutral for the first two years of World War I, entering on the side of the Allied powers from 27 August 1916 until Central Power occupation led to the Treaty of Bucharest in May 1918, before reentering the war on 10 November 1918. It had the most significant oil fields in Europe, and Germany eagerly bought its petroleum, as well as food exports.
Although considerable conflict took place outside Europe, the European theatre was the main theatre of operations during World War I and was where the war began and ended. During the four years of conflict, battle was joined by armies of unprecedented size, which were equipped with new mechanized technologies. The conflict left tens of millions dead or wounded.
The Partition of the Ottoman Empire was a geopolitical event that occurred after World War I and the occupation of Constantinople by British, French, and Italian troops in November 1918. The partitioning was planned in several agreements made by the Allied Powers early in the course of World War I, notably the Sykes–Picot Agreement, after the Ottoman Empire had joined Germany to form the Ottoman–German alliance. The huge conglomeration of territories and peoples that formerly comprised the Ottoman Empire was divided into several new states. The Ottoman Empire had been the leading Islamic state in geopolitical, cultural, and ideological terms. The partitioning of the Ottoman Empire after the war led to the domination of the Middle East by Western powers such as Britain and France, and saw the creation of the modern Arab world and the Republic of Turkey. Resistance to the influence of these powers came from the Turkish National Movement but did not become widespread in the other post-Ottoman states until the period of rapid decolonization after World War II.
The Kingdom of Bulgaria participated in World War I on the side of the Central Powers from 14 October 1915, when the country declared war on Serbia, until 30 September 1918, when the Armistice of Salonica came into effect.
The Ottoman Empire's entry into World War I began when two recently purchased ships of its navy, which were still crewed by German sailors and commanded by their German admiral, carried out the Black Sea Raid, a surprise attack against Russian ports, on 29 October 1914. Russia replied by declaring war on 1 November 1914. Russia's allies, Britain and France, declared war on the Ottoman Empire on 5 November 1914. The reasons for the Ottoman action were not immediately clear. The Ottoman government had declared neutrality in the recently started war, and negotiations with both sides were underway.
The Ottoman Empire was one of the Central Powers of World War I. It entered the war on 29 October 1914 with a small surprise attack on the Black Sea coast of Russia, which prompted Russia to declare war on 2 November 1914. Ottoman forces fought the Entente in the Balkans and the Middle Eastern theatre of World War I. The Ottoman Empire's defeat in the war in 1918 was crucial in the eventual dissolution of the empire in 1922.
The foreign policy of the Russian Empire covers Russian foreign relations from their origins in the policies of the Tsardom of Russia down to the end of the Russian Empire in 1917. Under the system tsarist autocracy, the Emperors/Empresses made all the main decisions in the Russian Empire, so a uniformity of policy and a forcefulness resulted during the long regimes of powerful leaders such as Peter the Great and Catherine the Great. However, several weak tsars also reigned—such as children with a regent in control—and numerous plots and assassinations occurred. With weak rulers or rapid turnovers on the throne, unpredictability and even chaos could result.
The diplomatic history of World War I covers the non-military interactions among the major players during World War I. For the domestic histories of participants see home front during World War I. For a longer-term perspective see international relations (1814–1919) and causes of World War I. For the following (post-war) era see international relations (1919–1939). The major "Allies" grouping included Great Britain and its empire, France, Russia, Italy and the United States. Opposing the Allies, the major Central Powers included Germany, Austria-Hungary, the Ottoman Empire (Turkey) and Bulgaria. Other countries also joined the Allies. For a detailed chronology see timeline of World War I.
Italy entered into the First World War in 1915 with the aim of completing national unity: for this reason, the Italian intervention in the First World War is also considered the Fourth Italian War of Independence, in a historiographical perspective that identifies in the latter the conclusion of the unification of Italy, whose military actions began during the revolutions of 1848 with the First Italian War of Independence.
French Third Republic (including colonial forces)
United Kingdom (including colonial forces)
Russian Empire (until March 1917 [lower-alpha 1] ) 
Soviet Russia (November 1917 - March 1918)
Kingdom of Serbia 
Kingdom of Italy [lower-alpha 2] (from May 1915) (including colonial forces)
Kingdom of Belgium (including colonial forces)
United States of America (after April 1917)
Kingdom of Montenegro 
Empire of Japan 
Portuguese Republic (March 1916 and after) (including Portuguese colonial forces)
Kingdom of Romania (August 1916 – May 1918, November 1918)
Kingdom of Greece (November 1916 for the Government of National Defence; June 1917 for the whole country)
Albania 
Brazil (October 1917 and after)
Armenia (May 1918 and after)
Czechoslovakia – See Czechoslovak Legions 
Finland (October 1918 and after)
Nepal (soldiers served under the British Indian Army)
Kingdom of Siam 
San Marino (June 1915 and after)
Sweden (June 1914-early 1916) (1918)
Andorra 
Bolivia (April 1917 and after)
China (August 1917 and after)
Costa Rica (May 1918 and after)
Cuba (April 1917 and after)
Ecuador (December 1917 and after)
Guatemala (April 1918 and after)
Liberia (August 1917 and after)
Haiti (July 1918 and after)
Honduras (July 1918 and after)
Nicaragua (May 1918 and after)
Panama (December 1917 and after)
Peru (October 1917 and after)
Uruguay (October 1917 and after)
