The protagonist of Morris's fable is Matthias 'Corvinus', king of Hungary 1458-90. He was elected king in 1458, aged only about fifteen, as the surviving son of John Hunyadi (d. 1456), who had been from the early J 440s the leading commander of the Hungarian forces against the advancing Ottoman Turks, whom he several times defeated, and also from 1444 effective regent of that kingdom while its king Ladislas II was under age. Hunyadi, who came from a Wallachian noble family, settled in Transylvania where his much-restored castle can still be seen. He was supposed in a legend, accepted by Morris but now discarded by historians, to have been an illegitimate son of Sigismund of Luxemburg, king of Hungary from 1387 and Holy Roman Emperor from 1410, who died in 1438. Hence the discontented noble calls Matthias 'son's son of a whore'. The Hunyadi family certainly, however, benefited from Sigismund's patronage.

Morris's comparison of Matthias to King Alfred refers to his achievements in war and peace, both in defending his country from dangerous invaders of a different religion, for Alfred the Danes, for Matthias the Turks, and in his endeavours to raise the cultural level of his people. When Matthias attained the throne, the Turkishadvance had recently reached the Danube (his father died just after defeating their siege of Belgrade), and he spent the early years of his reign stabilising his southern frontier with them, assisted by his establishment of an efficient mercenary arm, the Black Band whom Morris mentions, to supplement the feudal levies of the Hungarian aristocracy. After the mid 1460s, however, he stood on the defensive on that frontier, contenting himself with repelling occasional Turkish raids, while devoting most of his campaigning to attacking his Christian neighbours to the north and west: by his death in 1490 he had occupied Moravia, Silesia, and much of Austria.

From the middle of his reign Matthias also sought to bring to his country some of the cultural innovations of the developing Italian Renaissance, importing Italian artists to decorate his palace at Buda (destroyed during warfare with the Turks from the 16th century), attracting minor Italian 'humanists' to his court, and corresponding with Italian scholars, including Marsilio Ficino, the leading Florentine commentator on Plato's philosophy. (Morris probably makes the captain speaking to the king refer particularly to 'that Plato of thine' because that philosopher was known as the first to advocate community of property, at least for the ruling group in his imagined republic.) Matthias's most prominent cultural achievement, which might have brought him to the awareness of Morris as a lover of illuminated manuscripts, was his gathering from the 1470s, especially in the late 1480s, of a library of manuscripts, particularly of the Greek and Latin classics, many specially copied for him at Florence, and some elaborately decorated. (Whether Morris would have admired the Renaissance style used to adorn Matthias's books is perhaps doubtful.) The 'Bibliotheca Corviniana' as it was later styled may have included over 2,000 books, thus being one of the largest of its age in Europe. Slightly over 200, scattered through various mostly European libraries, survived the impact of the Turkish invasion of Hungary in 1526 and subsequent warfare.

The economic and social structure that Morris has imagined for his Hungarian kingdom is that of a typical feudal society with lords dominating and exploiting the peasantry. In practice, although Hungary was indeed controlled by a martial aristocracy divided into several ranks, the peasantry may not have been too heavily burdened, since they owed the lordsrents and some renders in kind, but little in the way of labour services, and in Matthias's time the taxation needed to support his professional army may have been a greater burden for them, but Morris would not have known this. Under Matthias's weaker successors the lords were able to increase the subjection of  their peasant tenants, provoking in 1513-14 a ferocious peasant revolt, repressed with equal savagery, its leader being tortured to death, of which Morris, who certainly knew of the German Peasant War of the early 1520s, might have heard.

Morris is correct about the importance of wine growing even in medieval Hungary, some of which, already then, as in the 19th century, coming from the 'Tokay' region, apparently sweet, was thought good enough to export to neighbouring countries. In his description of the vineyard running down to a stream, which his peasants so laboriously hoe, Morris may be looking back some twenty years to his account in 'Bellerophon  in Lycia' of the happier vintage festival so cruelly interrupted by the advent of the Chimera.

Possible Sources for the Tale:

Morris writes at its start as though he is modelling the tale on an actual story told about King Matthias, and it is hard to suppose that if he had simply invented it he would have chosen as its chief character a relatively obscure East European monarch. Moreover the few details he gives about the historical background are reasonably accurate. I suspect that he found it in the course of his reading, whether in whatever history dealing with Hungary he drew those details from, or in some work about manuscripts. (However the only 19th-century book specifically about Matthias's library, mentioned in Tanner's bibliography, was published in 1878 in German, which Morris did not easily read.) One possible intermediary source might be Carlyle's Frederick the Great, whose opening volume includes an account of the medieval electorate of Brandenburg, which Frederick's Hohenzollern ancestors obtained about 1415. A discussion of late medieval German politics might bring in Matthias, and Carlyle might happily report an anecdote showing social responsibility on his part. Tanner also mentions two early 19th-century books discussing the king's library that might have included tales about Matthias.

As for any original source for the story, the most likely seems an account in Latin by Galeozzo Marzio, one of Matthias's court 'humanists’, of the 'Sayings and Deeds of Matthias Corvinus', written for the king's son John. Marzio appears as 'Martius Galeotti', the astrologer to Louis XI of France in Scott's Quentin Durward, especially notes II and X, where the Scott-loving Morris could well have noticed him, and where his association with Matthias is noted; though that book does not appear in the list of Morris's early printed books in the last volume of the Collected Letters. But he is more likely to have found the tale in some intermediary work, and elaborated it to give a Socialist moral. There is also a history of Hungary, covering Matthias's reign, in Latin by Antonio Bonfini, another of his scholars. Morris does not seem to have had copies of either of these works in 1896 though he did by then own two copies of a jejune chronicle of Hungarian history printed in Germany in 1488.

Listed in M. Tanner, The Raven King (Yale UP, 2008), 216-24.