In a rousing style characteristic of Welsh heroic poetry, it describes a future where all of Brythonic peoples are allied with the Scots, the Irish, and the Vikings of Dublin under Welsh leadership, and together succeed in driving the Anglo-Saxons from Britain forever. Leaders of such ventures are always given names in heroic poetry, and in this case they are said to be Cadwallon and Cadwaladr, implicitly inviting the audience to connect them with two famous leaders from the distant past, Cadwallon ap Cadfan and Cadwaladr ap Cadwallon. The inclusion of the non-Celtic Vikings and the non-Brythonic Scots and Irish as full allies in a Welsh traditional poem is a remarkable oddity.
The poem is commonly described as an expression of Welsh frustration with the pragmatic, peaceful policies of Hywel Dda towards the then-ascendant Kingdom of Wessex. Edward the Elder (reigned 899 – 924) had gained acknowledged pre-eminence over almost all of the peoples south of the Firths of Clyde and Forth, including the Gaels, Vikings, English, Cornish, Welsh, and the Cumbrians. After he died and his son Æthelstan had become king (reigned 924 – 939), an alliance of the kingdoms of Dublin, Scotland, and Strathclyde rose against him and was defeated at the Battle of Brunanburh in 937. Out of keeping with their historical stance alongside the 'Men of the North' (Welsh: Gwŷr y Gogledd) and against the English, the Welsh under Hywel Dda had stood aside, neither helping their traditional compatriots (the men of Strathclyde) nor opposing their traditional enemies (the Saxons of Wessex).
The Armes Prydein is also significant as one of the earliest mentions of the prophet Myrddin Wyllt.
- Skene, William Forbes (1868a), The Four Ancient Books of Wales, I, Edinburgh: Edmonston and Douglas (published 1868) pp. 436–442.
- Skene, William Forbes (1868b), The Four Ancient Books of Wales, II, Edinburgh: Edmonston and Douglas (published 1868), pp. 123–129.
- Koch, John T., ed. (2005), Celtic Culture: A Historical Encyclopedia, ABL-CLIO (published 2006), ISBN 978-1-85109-440-0 p. 85
- "Armes Prydein Vawr" at the Celtic Literature Collective (in Welsh)
- "The Great Prophecy of Britain" at the CLC
- "Armes Prydain Bychan" at the CLC (in Welsh)
- "The Lesser Prophecy of Britain" at the CLC