Long before it became one of the world's most recognisable national flags, the red dragon of Wales was the loser of a fight — at least at first — in a legend built to explain a tower that simply would not stand.
According to the 9th-century Historia Brittonum and its later, more elaborate retelling by Geoffrey of Monmouth, the 5th-century British ruler Vortigern attempted to build a fortress in the mountains of Snowdonia, only to find its walls collapsing overnight no matter how many times his workers rebuilt them. His advisors told him the only remedy was to sprinkle the foundation with the blood of a boy born without a father.
Servants searching the land found such a boy: the young Merlin (Myrddin), who, brought before Vortigern, revealed the true cause of the tower's instability — hidden beneath the foundation was an underground pool containing two sleeping dragons, one red and one white, whose nightly struggle shook the ground and brought the walls down each time.
Once the pool was drained and the dragons revealed, they began fighting in earnest. Young Merlin interpreted the battle prophetically: the white dragon — representing the Saxon invaders then conquering Britain — would initially overpower the red dragon, representing the native Britons. But ultimately, Merlin foretold, the red dragon would prevail, a coded promise that the British people would eventually reclaim their land from Saxon rule.
An honest reading of the politics: this legend functions transparently as a piece of politically motivated nation-building myth, composed and preserved by Britons living under Saxon conquest, offering hope for eventual reversal dressed as ancient prophecy rather than as a documented historical event.
From legend to flag: the red dragon (Y Ddraig Goch) became closely associated with Welsh identity for centuries afterward, plausibly reinforced by genuine Roman-era military draco standards once carried by Romano-British troops, giving the symbol a possible root that predates the Vortigern legend itself. The red dragon was formally adopted as the official flag of Wales in 1959, giving this medieval prophecy a very concrete, still-flying modern legacy.