House of the Dragon is taking place much earlier in Game of Thrones’ timeline than previously expected, which now allows the prequel to better contextualize the warring Targaryen characters in their battle for the Iron Throne. Based on George R.R. Martin’s Targaryen family history book Fire & Blood, House of the Dragon’s central event is the much-chronicled Targaryen Civil War, the Dance of the Dragons. This feud took place between 129 AC and 131 AC, approximately 170 years before Game of Thrones’ timeline begins. However, House of the Dragon’s trailer has now teased the inclusion of certain events that take place decades earlier.
The trailer for House of the Dragon seems to depict Harrenhal, with the castle being significant during this era as the location where the Great Council of 101 AC is held. The Great Council at Harrenhal saw many high lords in Westeros decide who would be the king after the death of Jaehaerys I, as the majority of his heirs had predeceased him. With only his four grandchildren, Rhaenys, Viserys, Daemon, and Aemma, and their heirs bringing forth claims, the Great Council decided that Jaehaerys’ successor would be his previous heir Baelon’s eldest son, Viserys. This decision meant passing over his eldest grandchild Rhaenys’ son Laenor Velaryon, who would eventually marry House of the Dragon’s Rhaenyra Targaryen.
The Great Council at Harrenhal is apt to be the source of much contention between House Targaryen’s family members in House of the Dragon, so it makes much sense to include it early on in the series. If the House of the Dragon trailer’s Harrenhal tease truly does mean an early scene or flashback to the Great Council, the prequel’s timeline will be going back decades earlier than previously thought. While this means the timeline of House of the Dragon will be far more expansive than Game of Thrones', the prequel will greatly benefit from depicting these earlier events. The Great Council of 101 AC will set up the many feuds amongst the Targaryens in terms of Rhaenys and her son’s claim being passed over, King Viserys I ascending the throne, and the political marriages that spawned from this event. House of the Dragon has plenty of moving pieces just within the Targaryen family, so contextualizing it with events from decades before the Dance of the Dragons will help audiences to fully understand the roots and depth of such rivalries.
House of the Dragon’s earlier timeline also suggests that the prequel will feature a more focused deep dive into the character development of the Targaryens at play in the Dance of the Dragon. While it was already revealed that House of the Dragon would depict the teenage years of Rhaenyra Targaryen, the Great Council’s timeline allows the series to go further into how the decision for Jaehaerys’ successor impacted the dynamics and sentiments of the family’s future within House Targaryen. The Great Council’s inclusion will help to fully explore why Matt Smith’s Daemon Targaryen long considered himself Viserys’ successor, contextualize why the marriage between Rhaenyra and Laenor was so important, and further establish the Westerosi precedent of prioritizing a male heir over a female successor – a significant decision that would return for Rhaenyra’s claim to the throne over her younger half-brother Aegon II.
While Game of Thrones’ timeline only spanned from 298 AC to 305 AC, House of the Dragon will now seemingly exhaust the events from at least 101 AC to 131 AC, with the timeline perhaps extending even further to the beginning of Aegon III’s reign. This may suggest that the prequel series will have a much faster pace than Game of Thrones, though it’s likely that the timeline between 101 AC and 129 AC will only be depicted in quick flashbacks or prologues. However, even if House of the Dragon's characters spend a significant amount of time at the Great Council at Harrenhal or depicting Rhaenyra’s childhood, these moments are vital in terms of fully understanding the interfamily feuds at play, particularly for establishing which Targaryens will be seen as the heroes.