Ferdinand Viktor Albert Meinrad of Hohenzollern-Sigmaringen came from a family of dynastic tradition, as the son of the prince Leopold of Hohenzollern-Sigmaringen and of the Infanta of Portugal, Princess Antonia of Saxe-Coburg-Gotha. His father was the brother of King Carol I, the sovereign of Romania. As the latter did not have children, he named Ferdinand successor to the throne, which was stated in an act signed on 18 May 1881. Eight years later, on March 18, 1889, Ferdinand was officially declared the heir to the throne. After a military career, he settled in The Old Kingdom of Romania, made up of the principalities of Wallachia and Moldova (united in 1859), where he prepared himself under the direct supervision of King Carol I. On October 11, 1914, at the death of his uncle, he became sovereign.

With the outbreak of the First World War, Romanian politicians, with the approval of King Carol I, had adopted neutrality. After two years however, with the promise of the Entente countries (Great Britain, France, Russia, Italy) to recognise the legitimacy of the union of Transylvania and Bukovina with the Old Kingdom, the new sovereign accepted to join the war effort. Although he was a relative of the German imperial family, Ferdinand I decided, together with the majority of the members of the Crown Council, on August 14/27, 1916, that Romania should enter the First World War on the Entente side against Germany and Austria-Hungary, thus making the most important step for achieving the ideal of unification shared by most Romanians.

Attached to his adoptive country, Ferdinand overcame his origins and presided over the creation of Greater Romania. The ideal was difficult to achieve, however, because at that time Transylvania was under Austro-Hungarian rule and the Romanians, who were the oldest and most numerous inhabitants of the province, faced a difficult situation. The end of the First World War turned the dream into reality for Romanians. Thus, on December 1, 1918, the Great Union was established, and Transylvania was joined by both Bessarabia and Bukovina to be united with the Old Kingdom. The symbolic act that consecrated the union was the crowning ceremony of King Ferdinand I and Queen Marie as sovereigns of Greater Romania, which took place on 15 October 1922 in Alba Iulia.

Following this historic achievement, King Ferdinand also received the appellation Întregitorul (‘The Unifier’). His particular style of leadership and the reforms which were initiated and concluded during his reign – universal vote, agrarian reform, the Constitution of 1923, administrative unification – made him a beloved monarch and provided the necessary conditions for the consolidation of the new Romanian state created in 1918.