Battle of the Redgrass Field

The Battle of Redgrass Field was a military engagement fought approximately a century before the events of Game of Thrones. It was the final battle of the Blackfyre Rebellion and was where Daemon Blackfyre was slain and his attempt to unseat his half-brother King Daeron II Targaryen was defeated.

In the books
The Battle of Redgrass Field is detailed in flashback in the second of George R.R. Martin's Dunk and Egg prequel novellas, The Sworn Sword.

This battle took place in approx. 195 or 196 AL and was the concluding battle of the Blackfyre Rebellion. Daemon Blackfyre, the bastard son of King Aegon IV Targaryen by his cousin Daena, claimed that his half-brother Daeron II Targaryen was illegitimate, being born of a liaison between his mother and her other brother. This would give him, as Aegon IV's next-eldest and legitimised child, the right to the Iron Throne. Daeron II disputed this and the resulting civil war lasted more than a year, with the realm divided between the red dragon (the Targaryens) and the black (the Blackfyres).

The decisive battle came on a wide, nondescript field south-west of King's Landing. Daemon Blackfyre's forces gained the upper hand over the royalist army, with Daemon defeating Ser Gwayne Corbray of the Kingsguard in single combat. Whilst chivalrously dismounting to help his wounded foe from the battlefield, Daemon was slain by a volley of arrows fired by the Raven's Teeth, an elite archery formation led by his half-brother Brynden Rivers, popularly known as "Bloodraven". The Raven's Teeth caused immense damage to Daemon's army, slaying two of his sons as well. Daemon's other bastard half-brother, Aegor Rivers, known as "Bittersteel", led a cavalry charge which routed the Raven's Teeth and resulted in a duel between himself and Bloodraven that ended with Bloodraven losing an eye. However, Bloodraven's gambit allowed Prince Baelor "Breakspear" Targaryen and his brother Prince Maekar to arrive with substantial reinforcements, outflanking the committed Blackfyre army and destroying it. The number of deaths that day - more than ten thousand - resulted in the grass turning red from blood, giving the battle its name.

Bittersteel was able to flee the field with a loyal core of supporters, who subsequently fled across the Narrow Sea to the Free Cities. They later founded the Golden Company, a famous mercenary army, and attempted several more times to invade Westeros until being finally defeated in the War of the Ninepenny Kings more than fifty years later.