House of Hohenzollern in the context of "Romanian royal family"

The Kingdom of Romania (Romanian: Regatul României) was a constitutional monarchy that existed from 25 March [O.S. 13 March] 1881 with the crowning of prince Karl of Hohenzollern-Sigmaringen as King Carol I (thus beginning the Romanian royal family), until 1947 with the abdication of King Michael I and the Romanian parliament's proclamation of the Romanian People's Republic.

From 1859 to 1877, Romania evolved from a personal union of two principalities: (Moldavia and Wallachia) called the Unification of Moldavia and Wallachia also known as "The Little Union" under a single prince to an autonomous principality with a Hohenzollern monarchy. The country gained its independence from the Ottoman Empire during the 1877–1878 Russo-Turkish War (known locally as the Romanian War of Independence), after which it was forced to cede the southern part of Bessarabia in exchange for Northern Dobruja. The kingdom's territory during the reign of King Carol I, between 13 (O.S.) / 25 March 1881 and 27 September (O.S.) / 10 October 1914 is sometimes referred to as the Romanian Old Kingdom, to distinguish it from "Greater Romania", which included the provinces that became part of the state after World War I (Bessarabia, Banat, Bukovina, and Transylvania).

The German Empire (German: Deutsches Reich), also referred to as Imperial Germany, the Second Reich, or simply Germany, was the period of the German Reich from the unification of Germany in 1871 until the November Revolution in 1918, when Germany changed its form of government to a republic. The German Empire consisted of 25 states, each with its own nobility: four constituent kingdoms, six grand duchies, five duchies (six before 1876), seven principalities, three free Hanseatic cities, and one imperial territory. While Prussia was only one of the four kingdoms in the realm, it contained about two-thirds of the Empire's population and territory, and Prussian dominance was also constitutionally established, since the King of Prussia was also the German Emperor (Deutscher Kaiser).

The empire was founded on 18 January 1871, when the south German states, except for Austria, Switzerland and Liechtenstein, joined the North German Confederation. The new constitution came into force on 16 April, changing the name of the federal state to the German Empire and introducing the title of German Emperor for Wilhelm I, King of Prussia from the House of Hohenzollern. Berlin remained its capital, and Otto von Bismarck, Minister President of Prussia, became chancellor, the head of government. After 1850, the states of Germany had rapidly become industrialized. In 1871, Germany had a population of 41 million people; by 1913, this had increased to 68 million. A heavily rural collection of states in 1815, the now united Germany became predominantly urban. German factories were often larger and more modern than many of their British and French counterparts, but the preindustrial sector was more backward. The success of the German Empire in the natural sciences was such that one-third of all Nobel Prizes went to German inventors and researchers. During its 47 years of existence, the German Empire became an industrial, technological, and scientific power in Europe, and by 1913, Germany was the largest economy in continental Europe and the third largest in the world. Germany also became a great power, building the longest railway network of Europe, the world's strongest army, and a fast-growing industrial base. Starting very small in 1871, in a decade, the navy became second only to Britain's Royal Navy.

The Kingdom of Prussia (German: Königreich Preußen, pronounced [ˈkøːnɪkʁaɪç ˈpʁɔʏsn̩] ) was a German state that existed from 1701 to 1918. It played a significant role in the unification of Germany in 1871 and was a major constituent of the German Empire until its dissolution in 1918. Although it took its name from the region called Prussia, it was based in the Margraviate of Brandenburg. Its capital was Berlin.

The kings of Prussia were from the House of Hohenzollern. The polity of Brandenburg-Prussia, predecessor of the kingdom, became a military power under Frederick William, Elector of Brandenburg, known as "The Great Elector". As a kingdom, Prussia continued its rise to power, especially during the reign of Frederick II "the Great". Frederick the Great was instrumental in starting the Seven Years' War (1756–1763), holding his own against Austria, Russia, France and Sweden and establishing Prussia's dominant role among the German states, as well as establishing the country as a European great power through the victories of the powerful Prussian Army. Prussia made attempts to unify all the German states (excluding the German cantons in Switzerland) under its rule, and whether Austria would be included in such a unified German domain became an ongoing question. After the Napoleonic Wars led to the creation of the German Confederation, the issue of unifying the German states caused the German revolutions of 1848–1849, with representatives from all states attempting to unify under their own constitution. Attempts to create a federation remained unsuccessful and the German Confederation collapsed in 1866 when the Austro-Prussian War ensued between its two most powerful member states.

Prussia (/ˈprʌʃə/; German: Preußen [ˈpʁɔʏsn̩] ; Old Prussian: Prūsija) was a German state centred on the North European Plain that originated from the 1525 secularization act of the Prussian part of the State of the Teutonic Order. For centuries, the House of Hohenzollern ruled Prussia, expanding its size with the Prussian Army. Prussia, with its capital at Königsberg and then, when it became the Kingdom of Prussia in 1701, Berlin, decisively shaped the history of Germany. Prussia formed the German Empire when it united the German states in 1871. It was de facto dissolved by an emergency decree transferring powers of the Prussian government to German Chancellor Franz von Papen in 1932 and de jure by an Allied decree in 1947.

The name Prussia derives from the Old Prussians who were conquered by the Teutonic Knights – an organized Catholic medieval military order of German crusaders – in the 13th century. In 1308, the Teutonic Knights conquered the region of Pomerelia with Danzig. Their monastic state was mostly Germanised through immigration from central and western Germany, and, in the south, it was Polonised by settlers from Masovia. The imposed Second Peace of Thorn (1466) split Prussia into the western Royal Prussia, a province of Poland, and the eastern Duchy of Prussia, a feudal fief of the Crown of Poland until 1657. After 1525, the Teutonic Order relocated their headquarters to Mergentheim, but managed to keep land in Livonia until 1561. The union of Brandenburg and the Duchy of Prussia in 1618 led to the proclamation of the Kingdom of Prussia in 1701.

The Kingdom of Romania remained neutral throughout the first two years of World War I. They eventually entered the conflict on the side of the Entente from 27 August 1916 until insurmountable pressure from Central Powers - which had occupied two thirds of the country - led to an armistice being signed on 9 December 1917. Six months later, a crippling peace treaty was imposed on Romania, which the government ratified. King Ferdinand I refused to promulgate the treaty, hoping for an Allied victory on the Western Front. As the Central Power war efforts collapsed, Romania re-entered the war on 10 November 1918.

Romania was still a burgeoning state with great territorial ambitions at the onset of the war. It had achieved its independence following the Russo-Turkish War of 1877–1878, although millions of ethnic Romanians continued to reside outside the new nation's borders, particularly in Transylvania and Bessarabia, which were part of Austria-Hungary and Russia respectively. The Romanian monarchy, which was formed by members of the Hohenzollern dynasty, who were of Germanic origin, was sympathetic towards the cause of the Central Powers. The nation's political elite and the majority of the public favoured the Entente, as joining them would allow Romania to take Transylvania from Austria-Hungary, a region rich with natural resources and inhabited by a Romanian majority. Because of this social division and the general feeling that Romania still wasn't fully prepared for a war against a great power, the Romanians initially opted for neutrality.

Hohenzollern-Sigmaringen (German: Fürstentum Hohenzollern-Sigmaringen) was a principality in southwestern Germany. Its rulers belonged to the junior Swabian branch of the House of Hohenzollern. The Swabian Hohenzollerns were elevated to princes in 1623. The small sovereign state with the capital city of Sigmaringen was annexed to the Kingdom of Prussia in 1850 following the abdication of its sovereign in the wake of the revolutions of 1848, then became part of the newly created Province of Hohenzollern.

Wilhelm I (William I; William Frederick Louis; German: Wilhelm Friedrich Ludwig; 22 March 1797 – 9 March 1888) was King of Prussia from 1861 and German Emperor from 1871 until his death in 1888. A member of the House of Hohenzollern, he was the first head of state of a united Germany. He was regent of Prussia from 1858 to 1861 for his elder brother, King Frederick William IV. During the reign of his grandson Wilhelm II, he was known as Emperor Wilhelm the Great (German: Kaiser Wilhelm der Große).

The second son of Prince Frederick William and Louise of Mecklenburg-Strelitz, Wilhelm was not expected to ascend to the throne. His grandfather, King Frederick William II died the year he was born, and his father was crowned Frederick William III. Wilhelm fought with distinction during the War of the Sixth Coalition, and afterwards became a prominent figure within the Prussian Army. In 1840, his childless elder brother became King of Prussia, making him heir presumptive. Wilhelm played a major role in crushing the Revolutions of 1848 in Germany, although he was briefly forced into exile in England. Frederick William IV suffered a stroke in 1857 and was left incapacitated, and Wilhelm was formally named Prince Regent a year later. In 1861, Wilhelm ascended to the Prussian throne on his elder brother's death.

The monarchs of Prussia were members of the House of Hohenzollern who were the hereditary rulers of the former German state of Prussia from its founding in 1525 as the Duchy of Prussia. The Duchy had evolved out of the Teutonic Order, a Roman Catholic crusader state and theocracy located along the eastern coast of the Baltic Sea. The Teutonic Knights were under the leadership of a Grand Master, the last of whom, Albert, converted to Protestantism and secularized the lands, which then became the Duchy of Prussia.

The Duchy was initially a vassal of the Kingdom of Poland, as a result of the terms of the Prussian Homage whereby Albert was granted the Duchy as part of the terms of peace following the Prussian War. When the main line of Prussian Hohenzollerns died out in 1618, the Duchy passed to a different branch of the family, who also reigned as Electors of Brandenburg in the Holy Roman Empire. While still nominally two different territories, Prussia under the suzerainty of Poland and Brandenburg under the suzerainty of the Holy Roman Empire, the two states are known together historiographically as Brandenburg-Prussia.