(English: On the Ruin and Conquest of Britain) is a work written in Latin in the late fifth or sixth century by the British religious polemicist Gildas. It is a sermon in three parts condemning the acts of Gildas' contemporaries, both secular and religious, whom he blames for the dire state of affairs in sub-Roman Britain. It is widely acknowledged by historians that the text cannot be straightforwardly used to construct a reliable narrative history of fifth- and sixth-century Britain.; Michael Lapidge and David Dumville, eds., Gildas: New Approaches (Woodbridge: Boydell, 1984), pp. x-xi; Guy Halsall, Worlds of Arthur: Facts & Fictions of the Dark Ages (Oxford: Oxford University Press, 2013), pp. 53–55; James M. Harland, 'Rethinking Ethnicity and "Otherness" in Early Anglo-Saxon England,' Medieval Worlds 5 (2017), pp. 113–142, p.114, https://doi.org/10.1553/medievalworlds_no5_2017s113 It nevertheless is one of the most important sources for the history of Britain in the fifth and sixth centuries, as it is the only significant historical source for the period written by a near contemporary of the people and events described.
Part I contains a narrative of British history from the Roman conquest to Gildas' time; it includes references to Ambrosius Aurelianus and the Britons' victory against the Saxons at the Battle of Mons Badonicus. Part II is a condemnation of five kings for their various sins, including both obscure figures and relatively well-documented ones such as Maelgwn Gwynedd. Part III is a similar attack upon the British clergy of the age.
Date Gildas's work is of great importance to historians, because, although it is not intended primarily as history, it is almost the only surviving source written by a near-contemporary of British events in the fifth and sixth centuries. The usual date that has been given for the composition of the work is some time in the 540s, but it is now regarded as quite possibly earlier, in the first quarter of the sixth century, or even before that. The historian Karen George, in her study of Gildas' text, suggests a date range of –530 AD, while the historian Stephen Joyce argues for c. 483–485 AD.George, Karen, Gildas's De Excidio Britonum and the Early British Church, Studies in Celtic History 26, Boydell Press, 2009, p. 125; Joyce, Stephen J. The Legacy of Gildas: Constructions of Authority in the Early Medieval West, Studies in Celtic History 43, Boydell Press, 2022, p. 158. In the view of the historian Guy Halsall: There is some evidence for an "early Gildas", writing in the late fifth century. This includes Gildas' rhetorical education, his Latin style, his theological concerns, and a rereading of his historical section and his place within it. I tend towards this interpretation, although it cannot be proven. It is unlikely that Gildas wrote before 480/490 or much after about 550; beyond that we cannot go.
Despite this uncertainty, most scholars continue to favour a date c. 530–545, as supported by reports of the death of Gildas in the various Welsh and Irish annals: the Annales Cambriæ gives the year of his death as 570, while the Annals of Tigernach dates his death to 569. Andrew Breeze argues that Gildas was writing De Excidio in 536, in the middle of the extreme weather events of 535–536, because he mentions a "certain thick mist and black night" which "sits upon the whole island" of Britain. Breeze's hypothesis is disputed.Johnson, F.; "537 and Camlann" in "Transactions of the Cumberland and Westmoreland Antiquarian & Archaeological Society", Volume 19 (2019), 131–140 Stephen Joyce argues that arguments in favour of close dating are based on circular reasoning, and proposes returning to the broad range accepted in the twentieth century of 479–550 AD.Joyce, Stephen J., "Dating Gildas", Journal of the Australian Early Medieval Association 19.2, pp. 123-142, 2023
Gildas' intent in his writing was to preach to his contemporaries in the manner of an Old Testament prophet, not to write an account for posterity. Thus, he gives historical details where it serves his purpose; for instance, he offers one of the first descriptions of Hadrian's Wall and perhaps the Antonine Wall, though his account of their history appears to be inaccurate.Koch, p. 808.Gransden, p. 4. However, he omits details where they do not contribute to his message; he is consistently vague, giving few names and no firm dates.Gransden, p. 5. Nonetheless, De Excidio remains an important work not only for medieval history but also for British history in general, as it is one of the few works written in Britain to survive from the fifth or sixth centuries.
In a convoluted passage in , Gildas can be interpreted as equating the year of his birth with the same year as the Battle of Mons Badonicus, which might have taken place in 482 AD.Ó Cróinín, Dáibhí and McCarthy, Daniel. "The "Lost" Irish 84-year Easter Table Rediscovered", Peritia, 6–7 (1987–1988): 227–242.
Manuscripts and editions The oldest manuscript of the De Excidio is Cottonian MS. Vitellius A. VI, of the tenth century, damaged by fire in 1731, but used by Theodor Mommsen in his edition nevertheless. Other manuscripts include the Avranches public library MS. No. 162 of the twelfth century, the Cambridge University Library MS. Ff. I. 27 of the twelfth century, and the Cambridge University Library MS. Dd. I. 17 of c. 1400. Cambridge Ff. I. 27 is the recension of a certain Cormac and differs sharply from the other manuscripts in that it contains a shortened form of various parts and has many textual readings peculiar to itself. The oldest attestation of Gildas's work is actually found in the extensive quotations and paraphrases of the De Excidio made by Bede in his Ecclesiastical History of the English People, the earliest manuscripts of which date to the eighth century.
Gildas's treatise was first published in 1525 by Polydore Vergil but with many avowed alterations and omissions. In 1568 John Joscelyn, secretary to Archbishop Parker, issued a new edition of it more in conformity with manuscript authority; and in 1691 a still more carefully revised edition by Thomas Gale appeared at Oxford. It was frequently reprinted on the Continent during the 16th century, and once or twice since. The next English edition, described by August Potthast as editio pessima, was published by the English Historical Society in 1838, and edited by the Rev. J. Stevenson. The text of Gildas founded on Gale's edition collated with two other manuscripts, with elaborate introductions, is included in the Monumenta Historica Britannica. Another edition is in Arthur West Haddan and William Stubbs, Councils and ecclesiastical documents relating to Great Britain and Ireland (Oxford, 1869); the latest edition is that by Mommsen in Monumenta Germaniae Historica auct. antiq. xiii. (Chronica min. iii.), 1898. The text as it is used today is thus a scholarly reconstruction; the prime witness and possibly the entire manuscript stemma may not actually preserve the original page order of the autograph.Rosenbaum, S.; "Evidence of Transmission Errors Affecting the Text of Gildas's De Excidio" in Peritia, Journal of the Medieval Academy of Ireland, Volume 31 (2021)
Summary Part I The first part consists of Gildas' explanation for his work and a brief narrative of Roman Britain from its conquest under the principate to Gildas' time:
Concerning her obstinacy, subjection and rebellion, about her second subjection and harsh servitude; concerning religion, of persecution, the holy martyrs, many heresies, of tyrants, of two plundering races, concerning the defense and a further devastation, of a second vengeance and a third devastation, concerning hunger, of the letter to Agitius [usually identified with the patrician Flavius Aetius], of victory, of crimes, of enemies suddenly announced, a memorable plague, a council, an enemy more savage than the first, the subversion of cities, concerning those whose survived, and concerning the final victory of our country that has been granted to our time by the will of God.
Part I is the earliest source to describe the invitation by the Roman authorities of the Saxons to Britain, which Gildas describes using language closely related to Roman legal processes for settling barbarian foederati.Ian N. Wood, The End of Roman Britain: Continental Evidence and Parallels, in: Lapidge and Dumville, Gildas: New Approaches, pp. 20-21; James M. Harland, 'Rethinking Ethnicity and "Otherness" in Early Anglo-Saxon England,' Medieval Worlds 5 (2017), pp. 113–142, p. 123. He is also particularly notable as the earliest source to mention Ambrosius Aurelianus, an important figure of British tradition credited with turning the tide against the Anglo-Saxon conquest. It also contains the earliest mention of the Britons' victory at the Battle of Mons Badonicus.
It is a matter of dispute whether Gildas named the "proud tyrant" (superbus tyrannus) who invited the Saxons to Britain as Vortigern, as not all manuscripts contain the name. Theodor Mommsen believed that Gildas did not use the name Vortigern, and that in those manuscripts where it appears, it is an interpolation derived from Bede's Ecclesiastical History. Mommsen's 1898 edition of the text in Monumenta Germaniae Historica omits it, and his view has been influential in later scholarship. Theodor Mommsen (ed.), Gildas, De Excidio et Conquestu Britanniae. MGH:AA 13 (Berlin: Weidmann, 1898), 16, 38, fn. 12. Some scholars, such as David Dumville or Bernard Bachrach, preferring to rely on the continental manuscripts rather than MS. Vitellius A. VI, have argued that the possibility remains that Vortigern is original to Gildas.David Dumville, 'Sub-Roman Britain: History & Legend,' History 62:205 (1977), 173–192, 183–185; Bernard S. Bachrach, 'Gildas, Vortigern, and Constitutionality in Sub-Roman Britain,' Nottingham Medieval Studies 32 (1988), 126–140, 138. Others have followed Mommsen's interpretation on the absence of Vortigern,Guy Halsall, Worlds of Arthur: Facts & Fictions of the Dark Ages (Oxford: Oxford University Press, 2013), p. 60 or provided further reasons to dispute an association of the "proud tyrant" with Vortigern. Flint F. Johnson, 'Gildas's Legendary History of Post-Roman Britain,' Journal of Religious History, Literature, and Culture 11:1 (2025), pp. 1–24, pp. 13–14. Scholars generally acknowledge that the matter cannot be settled without the completion of a new edition.E.A. Thompson, 'Gildas and the History of Britain,' Britannia 10 (1979), pp. 203–226, p. 216, fn. 79; Kenneth Jackson, 'Varia: II, Gildas and the names of the British princes,' Cambrian Medieval Celtic Studies 3 (1982), pp. 30–40, p. 40.
Part II
The second part consists of a condemnation of five British kings, and as it is the only contemporary information about them, it is of particular interest to scholars of British history. Gildas swathes the condemnations in allegorical beasts from the Book of Daniel and the Book of Revelation, likening the kings to the beasts described there: a lion, a leopard, a bear, and a dragon.Daniel VII-3 – VII-7 The kings excoriated by Gildas are:
"Constantine the tyrannical whelp of the unclean lioness of Damnonia"., De Excidio, sections 28 and 29 (in English), De Excidio, sections 28 and 29 (in Latin); "thou lion's whelp Aurelius Conanus"., De Excidio, section 30 (in English);, De Excidio, section 30 (in Latin) "Vortipore ... who like to the spotted leopard ... tyrant of the Demetians";, De Excidio, section 31 (in English), De Excidio, section 31 (in Latin) "Cuneglasse ... thou bear"., De Excidio, section 32 (in English);, De Excidio, section 32 (in Latin) "dragon of the island ... Maglocune"., De Excidio, sections 33–35 (in English), De Excidio, sections 33–35 (in Latin)