The House of Habsburg provided Holy Roman Emperors in a continuous line of father to son, brother or grandson, from Frederick III in the mid-fifteenth century to Leopold I in the eighteenth. Towards the end of his reign and two years into the War of the Spanish Succession, Leopold formulated a Mutual Pact of Succession with his sons. Signed on 12 September 1703, the pact agreed that Joseph, later Joseph I, his elder son, would succeed to the core Habsburg dominions of Austria, Hungary, Croatia and Bohemia, while Charles, his younger son, would claim Spain and its territories in Europe and Spanish America. The pact also agreed their respective line of succession, with each committing to being succeeded by his own son. However, should there fail to be a male heir in either line, the surviving brother would succeed instead. If neither brother produced a male heir, Joseph’s daughters would take precedence and inherit the Habsburg estates as a whole.

Joseph I died in 1711 with no male heirs. Charles inherited and was elected Holy Roman Emperor as Charles VI. Two years later the War of the Spanish Succession ended with the Treaties of Utrecht and Rastatt signed respectively in 1713 and 1714. But Spain was not absorbed by either the French or Habsburg Empires; it was instead settled that Philip, Duc d’Anjou, Louis XIV’s grandson, would be crowned king of Spain with the proviso that he renounce his right to the French throne and thereby void the possibility of a single monarch uniting Spain and France. He was also forced to relinquish territory. Austria gained the kingdoms of Naples and Sardinia, and the major part of Milan and the Spanish Netherlands. Sicily went to the Duke of Savoy. And Gibraltar and Minorca were ceded to Britain, which was also granted trading access to Spain’s Latin American colonies.

In the wake of the post-war pan-European settlement, Charles VI formally abandoned the Mutual Pact of Succession and promulgated a decree that established new parameters. Known as the Pragmatic Sanction, it dictated that the Habsburg estates would be inherited by his eldest son but should there be no male heir the estates would pass not to Joseph I’s daughters but to his own. Only if such daughter or daughters died without issue would the estates revert to Joseph I’s daughters and their descendants. And in the event that a daughter succeeded, her husband would be eligible for election as Holy Roman Emperor.

The hereditary territories that comprised the Habsburg dominions were governed separately with different laws of succession and Charles VI sought to ensure that the Pragmatic Sanction would be recognised in each. The territories were advised of the terms formally in March 1720 and each signified their consent with the last, Fiume, signing an agreement in 1725. Notwithstanding the problems raised by Salic law, the mediaeval Germanic legal code that stipulated that inheritance should follow the male line, the German states also conformed, albeit that Saxony and Bavaria later reneged. The Prince Elector of Saxony had married Maria Josepha, Joseph I’s elder daughter, in 1719, and in 1722 the Prince Elector of Bavaria wed Maria Amalia, his younger. Despite renouncing their claims, both later asserted a right of inheritance.

Charles VI and his wife, Elisabeth Christine, had a son in 1716, but he died within a year of birth. Their next two children were daughters: Maria Theresa, born in 1717, and Maria Anna, in 1718. Royal conception was thereafter problematic and with an increasingly slim prospect of a male heir, Charles VI became obsessed with getting the agreement of Europe’s major powers to uphold the Pragmatic Sanction. His fixation opened Austria to political blackmail not only from France but also Prussia and Spain, which wanted the return of the territories it had ceded to Austria.

The Pragmatic Sanction was not a simple matter of Habsburg inheritance. It had a direct and substantial impact on the balance of political power in Europe. Austria, the seat of Habsburg influence, ruled or controlled a swathe of territories from the Austrian Netherlands, Milan, Tuscany and Naples, to a stretch of Central and Eastern Europe from the Tyrol, Bohemia and Silesia, to Hungary and Transylvania. And although the various prince-electors, lords and bishops within the German states who owed their allegiance to the Holy Roman Emperor had de facto independence within their territories, Vienna’s influence was sizable nonetheless.

The Pragmatic Sanction was eventually accepted by most European states, albeit in some instances in name only. And in recognition that the person most likely to succeed Charles VI as Holy Roman Emperor would be Maria Theresa’s consort, diplomatic attention focused on the sole candidate, Francis Stephen, the oldest surviving son of the Duke of Lorraine. He had been selected by Charles following the death of his older brother, Léopold Clément, and in 1723 was summoned to live and be educated at the Habsburg court in Vienna. Francis would become Duke of Lorraine in his own right soon afterwards and be courted politically by France and Britain.