Leading up to the finale of House of the Dragon season 3, all signs indicated that the Greens were about to meet a horrifying end. Rhaenyra Targaryen (Emma D'Arcy) and Daemon Targaryen (Matt Smith) managed to raise a land army large enough to take over Tumbleton—the same town that Ormund Hightower (James Norton) and Daeron Targaryen (Benjamin Evan Ainsworth) were using as a shelter. Furthermore, the Blacks had six dragons of fighting age in their ranks. Surely, nothing could go wrong for them, right?
Unfortunately for the queen of the Seven Kingdoms, Ulf the White (Tom Bennett) decided to betray her and used his dragon to burn most of her army. This was a catastrophic event that managed to turn the tide of the war, but it wasn't nearly as bad as it could've been. In George R. R. Martin's novel Fire & Blood, Ulf wasn't the only one to rise against the queen, as Hugh the Hammer (Kieran Bew) followed in his footsteps. The two joined forces with Daeron Targaryen to burn most members of the Blacks present during the First Battle of Tumbleton.
Fans had initially speculated that Hugh's betrayal in the TV show was merely set up during the finale of House of the Dragon season 3, especially considering that his wife, Kat (Ellora Torchia), died at the hands of Rhaenyra's army. However, it turns out he did actually betray his queen, but in a much more subtle way.
During an interview with Collider, House of the Dragon showrunner Ryan Condal revealed that Hugh's treason was represented by his disobedience towards Rhaenyra's orders:
"Did Hugh not betray Rhaenyra by disobeying her orders, abandoning his post in King's Landing, showing up to a war to which he was not invited, parking his dragon, and refusing aid when everything went to hell? Ulf's betrayal was felt more acutely due to the direct outcome, but do not discount Hugh's own treason."
After sending her husband/uncle to lay siege to Tumbleton, Rhaenyra ordered two of her six dragonriders to guard the Dragonpit located in King's Landing, and Hugh was among them. After all, it is well known that the Targaryens' true power lies in their ability to ride dragons into battle and burn their enemies. So, if the Greens were to attack the Dragonpit while the Battle of Tumbleton was ensuing, Rhaenyra's reign would've ended before it could've truly taken off. So the fact that Hugh left this place unprotected will certainly not sit well with the queen.
It's worth noting that Hugh chose to ignore his direct orders for very good reasons. Knowing that his wife was living in Tumbleton, he wanted to save her from harm before all hell broke loose. He didn't go against Rhaenyra's wishes to spite her, but rather to protect his own wife. With that in mind, there's also a case to be made that he didn't "betray" the queen, but the rest of the Seven Kingdoms are unlikely to look at the situation this same way.
Additionally, just because Hugh's "betrayal" didn't result in the deaths of hundreds doesn't mean he won't act more violently moving forward. At this point, he has lost his daughter and his wife, and Rhaenyra hasn't given him the promised house on Rhaenys Hill. To make matters more complicated, the queen could very well label him as a traitor due to his disobedience, giving him the final motivation necessary to completely turn against the Blacks.
Condal also teased that Hugh may not be as innocent as he seems at first sight, and hinted that we'll see a darker side of his character in season 4:
"Outwardly, Hugh might seem like a much more honorable man than Ulf, but this man has only ever acted out of self-interest. He never had a stake in this war or Rhaenyra's claim outside what suited his ambitions. And now one of the two things he cared about (his wife) is a casualty of this war."
In Fire & Blood, Hugh even decides that he should be King of the Seven Kingdoms and eventually fights for that title. However, there's still a gap between that iteration of the character and the one we saw in House of the Dragon season 3, so it will be interesting to see how far he can descend into madness when season 4 finally comes our way.
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