George R.R. Martin has released an excerpt of his upcoming book, "The World of Ice and Fire," which follows the history of Westeros, including a detail description of the infamous dragons.

The excerpt includes events from Daenerys Targarye's ancestor, Aegon Targaryen, and he used dragons to take over Westeros. Check out a snippet of the excerpt below:

Aegon Targaryen's conquest of the Seven Kingdoms did not take place in a single day. More than two years passed between Aegon's landing and his Oldtown coronation . . . and even then the Conquest remained incomplete since Dorne remained unsubdued. Sporadic attempts to bring the Dornishmen into the realm continued all through King Aegon's reign and well into the reigns of his sons, making it impossible to fix a precise end date for the Wars of Conquest.

Even the start date is a matter of some misconception. Many assume, wrongly, that the reign of King Aegon I Targaryen began on the day he landed at the mouth of the Blackwater Rush, beneath the three hills where the city of King's Landing eventually stood. Not so. The day of Aegon's Landing was celebrated by the king and his descendants, but the Conqueror actually dated the start of his reign from the day he was crowned and anointed in the Starry Sept of Oldtown by the High Septon of the Faith. This coronation took place two years after Aegon's Landing, well after all three of the major battles of the Wars of Conquest had been fought and won. Thus it can be seen that most of Aegon's actual conquering took place from 2-1 BC, Before the Conquest.

You can read the George R.R. Martin's full "The World of Ice and Fire" excerpt here.  "Game of Thrones" the HBO series airs on Sundays at 9 p.m. EST.