The following rendition of events are taken from Geoffrey of Monmouth's The History of the Kings of Britain. It is a brief outline of Geoffrey's chapters which concern King Arthur. You can find the full version of the text translated into English here: Arthurian Passages from Geoffrey of Monmouth
Events which unfold regarding King Arthur begin long before he is born. They start with the prophecies of Merlin.
King Vortigern watches two dragons fight, one white one red. The white dragon defeats the red and Vortigern asks Merlin what this means. Merlin prophecises the invasion of Britain by the Saxon nation as symbolised by the defeat of the red dragon. He prophesises that two brothers Uther Pendragon and Aurelius Ambrosius will come for Vortigern to avenge their father whom Vortigern killed. Merlin prophesises the crowning of Aurelius as the King of Britain and that peace shall reign.Aurelius Ambrosius, being anointed king of Britain, burns Vortigern besieged in a tower.
As Merlin foretold Aurelius Ambrosius lands on the shores of Britain and lays seige. Vortigen retreats but is trapped in his fortress. Aurelius sets light to the tower and thus avenges his father
A comet presignifies the reign of Uther
A comet passes over the skies and Uther summons Merlin to foretell the meaning of the comet. Merlin tells Uther of Aurelius' death and foretells that Uther will reign as King of Britain.
Uther, falling in love with Igerna, enjoys her by the assistance of Merlin's magical operations. Merlin aides Uther by giving him an illusionary appearance of Duke Gorles (Igraine's husband). He sneaks into the castle and beds Igraine. King Arthur is conceived.
Thus the legend of Tintagel Castle is born.
Uther marries Igerna (Igraine) and have a son named Arthur (later King Arthur) and a daughter, Anne. Uther drinks from a spring poisoned by the Saxons and dies.
Arthur succeeds him and becomes King Arthur. Arthur then besieges Colgrin. King Arthur defeats the Saxons and makes them his tributories. King Arthur supposedly kills 470 Saxons in one battle.
Arthur adds Ireland, Iceland, Gothland, and the Orkneys to his government.
Arthur subdues Norway, Dacia, Aquitaine, and Gaul.
It is here according to other writers that Arthur first refers to his Kingdom proper, its base at Camelot (supposedly near Winchester).
King Arthur marries Lady Guinevere
War with the Romans begin.
Lucius Tiberius calls together the eastern kings against the Britons.
Arthur commits to his nephew Modred the government of Britain. His dream at Hamo's Port.
The battle between King Arthur and Lucius Tiberius.
Lucius Tiberius being killed, the Britons obtain the victory.
News is brought to King Arthur that his nephew Modred, to whose care Arthur had entrusted Britain, had commited treason by declaring himeslf king and that queen Guanhumara, in violation of her first marriage, had wickedly married him.
Arthur returns to Britain and battles Morded. Morded is defeated and flees to Winchester.
Modred, after being twice besieged and routed, is killed. Arthur, being wounded, gives up the kingdom to Constantine.
Arthur is mortally wounded in the battle against Mordred and sails to the Isle of Avalon to be cured. He gives up the crown of Britain to Constantine, the son of Cador, duke of Cornwall.
To be continued.....