Regnal numbers are ordinal numbers—often written as Roman numerals—used to distinguish among persons with the same regnal name who held the same office, notably kings, queens regnant, popes, and rarely princes and princesses.
It is common to start counting either since the beginning of the monarchy, or since the beginning of a particular line of state succession. For example, Boris III of Bulgaria and his son Simeon II were given their regnal numbers because the medieval rulers of the First and Second Bulgarian Empire were counted as well, although the recent dynasty dates only back to 1878 and is only distantly related to the monarchs of previous Bulgarian states.Ian Mladjov, "Reconsidering Agatha, wife of Eadward the Exile," The Plantagenet Connection Summer/Winter 2003: 1-85, with sample pedigree at 78-85. available online. On the other hand, the kings of England and kings of Great Britain and the United Kingdom are counted starting with the Norman Conquest. That is why the son of Henry III of England is called Edward I, even though there were three English monarchs named Edward before the Conquest (they were distinguished by epithets instead).
Sometimes legendary or fictional persons are included. For example, the Swedish kings Eric XIV (reigned 1560–68) and Charles IX (1604–11) took ordinals based on a fanciful 1544 history by Johannes Magnus, which invented six kings of each name before those accepted by later historians. A list of Swedish monarchs, represented on the map of the Estates of the Swedish Crown, produced by French engraver (1673–1721) and published in Paris in 1719, starts with Canute I and shows Eric XIV and Charles IX as Eric IV and Charles II respectively; the only Charles holding his traditional ordinal in the list is Charles XII. Also, in the case of Emperor Menelik II of Ethiopia, he chose his regnal number with reference to a mythical ancestor and first sovereign of his country (a supposed son of biblical King Solomon) to underline his legitimacy into the so-called Solomonic dynasty.
Examples of monarchical ordinals
Monarchs with the same given name are distinguished by their ordinals: Kings Umberto I and Umberto II of Italy Empresses Catherine I and Catherine II of Russia Princes Rainier II and Rainier III of Monaco Popes Benedict XV and Benedict XVI
Ordinals may also apply where a ruler of one realm and a ruler of that realm's successor state share the same name: Queens Elizabeth I of England and Elizabeth II of the United Kingdom Kings Alfonso XI of Castile and Alfonso XII of Spain Kings Victor Emmanuel I of Sardinia and Victor Emmanuel II of Italy Kings Peter I of Serbia and Peter II of Yugoslavia
Double names Practice varies where monarchs go by two or more given names. For Swedish monarchs, the ordinal qualifies only the first name; for example, Gustav VI Adolf, known as "Gustav Adolf", was the sixth Gustav/Gustaf, but the third Gustav Adolf. By contrast, the Kingdom of Prussia was ruled in turn by Friedrich I, Friedrich Wilhelm I, Friedrich II, and Friedrich Wilhelm II; and later by Wilhelm I. Likewise Pope John Paul I, who chose his double name to honour predecessors John XXIII and Paul VI, and was succeeded by John Paul II.
Ordinals for non-reigning royalty In any case, it is usual to count only the monarchs or heads of the family, and to number them sequentially up to the end of the dynasty. A notable exception to this rule is the German House of Reuss. This family has the particularity that every male member during the last eight centuries was named Heinrich, and all of them, not only the head of the family, were numbered. While the members of the elder branch were numbered in order of birth until the extinction of the branch in 1927, the members of the younger line were (and still are) numbered in sequences that began and ended roughly as centuries began and ended. This explains why the current (since 2012) head of the Reuss family is called Heinrich XIV, his late father Heinrich IV and his sons Heinrich XXIX and Heinrich V.
It is rare, but some German princely families number all males whether head of the family or not; for example, Hans Heinrich XV von Hochberg was preceded as Prince of Pless by Hans Heinrich XI and succeeded by Hans Heinrich XVII; the ordinals XII, XIII, XIV, and XVI were borne by von Hochbergs who were not Prince of Pless. Similarly for the House of Reuss, where all men were numbered Heinrichs and some were reigning Princes of Reuss-Gera or Reuss-Greiz.
Pretenders and rulers of formerly deposed dynasties are often given regnal numbers as if non-reigning pretenders had actually ruled. For example Louis XVIII of France took a regnal number that implicitly asserts that Louis XVII had been king, though he never reigned; his pretendership was during the French First Republic. A similar case is that of Napoleon III whose regnal number implicitly asserts a ruling Napoleon II. Louis XVIII numbered his regnal year from the death of Louis XVII, something Napoleon III never did.
History Almost all West European monarchs and popes after medieval times have used ordinals. Ordinals are also retrospectively applied to earlier monarchs in most works of reference, at least as far as they are not easy to distinguish from each other by any other systematical means. In several cases, various sorts of "semi-regnal" members of dynasties are also numeraled, to facilitate their individuality in works of reference – in cases such as co-regents, crown princes, succession-conveying consorts, prime ministers and deputy monarchs. In the first centuries after the Middle Ages, the use was sometimes sporadic, but became established by the 18th century. In the past couple of centuries, European monarchs without an official ordinal have been rarities.
As a rule of thumb, medieval European monarchs did not use ordinals at their own time, and those who used were rarities and even their use was sporadic. Ordinals for monarchs before the 13th century are anachronisms, as are also ordinals for almost all later medieval monarchs. Still, they are often used, because they are a practical way of distinguishing between different historical monarchs who had the same name.
Popes were apparently the first to assume official ordinals for their reigns, although this occurred only in the last centuries of the Middle Ages. It is clear, from renumberings of Popes John XV–XIX and Popes Stephen II–IX, that as of the 11th century the popes did not yet use established ordinals. The official, self-confirmed numbering of John XXI means that at latest from the 13th century the popes did take official ordinals in their accession.
Emperor Frederick II, King Charles II of Naples, King Premislas II of Poland and King Magnus VI of Norway (as Magnus IV) evidently used ordinals sometimes during their reign. In the 14th century, Emperor Charles IV sometimes used that ordinal. Presumably, use of the ordinal of king Frederick III of Sicily also is contemporaneous. The royal chroniclers of the Abbey of Saint-Denis were using ordinals to refer to the French kings as early as the thirteenth century with the practise entering common usage among royalty and the nobility by the late fourteenth century. The British tradition of consistently and prevalently numbering monarchs dates back to Henry VIII and Mary I; however, sporadic use occurred at least as early as the reign of Edward III. Some early accounts of Edward I number him the fourth, thus including the three pre-Norman Edwards.
The long history of the papacy has led to difficulties in some cases. For example, Stephen was only pope for three days before dying of apoplexy, and was never consecrated. Because not all list-makers count him as having been pope (as Stephen II), there has been some confusion in regard to later popes who chose the name Stephen. Later Stephens are sometimes numbered with parentheses, e.g., his immediate successor (in name) is denoted either Stephen (II) III or Stephen III (II). The church did consider Stephen II a pope until 1960, when he was removed from the list of popes in 1961. The history of the numbering of popes taking the regnal name "John" is even more convoluted, owing to the long history of popes taking the name (a common name, chosen frequently to honour the Apostle), bad record-keeping, and political confusion; among other results, the regnal name "John XX" is completely skipped under all reckonings.
Personal unions In the case of personal unions, some monarchs have had more than one ordinal, because they had different ordinals in their different realms. For instance, Charles XV of Sweden was also king of Norway, but in Norway he went under the name Charles IV. The Swedish-Norwegian union was in force 1814–1905 and both realms had had kings called Charles before the union, but Sweden had had more kings by that name.
In the event of one kingdom achieving independence from another but retaining the same monarch, the monarch often retains the same number as was already used in the older realm. King Christian X of Denmark thus became King Christian X of Iceland when Iceland became an independent kingdom in personal union with Denmark in 1918. The same is true for Commonwealth realms, where the monarch retains the regnal number from the British line of monarchs (see below).
Ordinals and the British Acts of Union 1707
Beginning in 1603, when England and Scotland began to share a monarch but were still legally separate realms, their monarchs were numbered separately. The king who began the personal union was James VI of Scotland who was also James I of England, and his name is often written (especially in Scotland) as James VI and I. Similarly, his grandson is James VII and II. Mary II's ordinal coincidentally relates to both her predecessors Mary I of England and Mary, Queen of Scots; her co-sovereign husband is William III and II (here the English number is first). Charles I and Charles II had a name not used in either country before 1603.
Acts of Union
After the realms were united with the Acts of Union 1707, separate numbers were not needed for the next five monarchs: Anne and the four Georges. However, when William IV acceded in 1830, he was not called William III in Scotland. (George Croly pointed out in 1830 the new king was William I, II, III, and IV: of Hanover, Ireland, Scotland, and England respectively.) Nor were Edward VII and Edward VIII known as Edward I and Edward II (or possibly II and III, if one counts the disputed reign of Edward Balliol) of Scotland. These kings all followed the numbering consistent with the English sequence of sovereigns (which, incidentally, was also the higher of the two numbers in all occurring cases). This was not without controversy in Scotland, however; for example, Edward VII's regnal number was occasionally omitted in Scotland, even by the established Church of Scotland, in deference to protests that the previous Edwards were English kings who had "been excluded from Scotland by battle". (Subscription required)