When Bertholdt transformed into the Colossal Titan and kicked open the gates of Wall Maria at Shiganshina in 845, the Wall Titans were still sealed and dormant inside the Walls themselves. King Karl Fritz had used the Founding Titan roughly a century earlier to create and harden tens of millions of these Abnormal Titans (which resemble smaller Colossals) into the concentric structures of Walls Maria, Rose, and Sina, leaving them immobile due to the lack of sunlight and the royal vow that kept them in place as a passive deterrent. They played no role in the initial breach because only the Founding Titan’s power could unharden the Walls and command them to march—something that didn’t happen until Eren activated the Rumbling years later. The gates were simply the vulnerable entry points the Warriors exploited with the Colossal and Armored Titans, allowing regular Pure Titans from outside to pour in while the Wall Titans stayed embedded and inactive throughout the fall of Shiganshina and the later Trost incident.

Eren didn’t spare Bertholdt because he couldn’t—or rather, he actively refused to. Through the Attack Titan’s ability to peer into and influence past events via the Paths, future Eren specifically directed Dina’s Pure Titan to bypass Bertholdt and devour Carla instead. This wasn’t some oversight or pure sadism; it was a deliberate, timeline-locking choice. If Dina had eaten Bertholdt, she would have inherited the Colossal Titan while still possessing royal blood. That would have given Grisha (and later Eren) an earlier, cleaner route to the Founding Titan’s full power without needing to orchestrate the entire 13-year cycle of hatred, the fall of Wall Maria, and the specific chain of events that put Armin in position to eat Bertholdt later. The future Eren had already seen—and accepted—would have collapsed. The tragedy is that Eren did choose his mother’s death. In the Paths, he admits he directed Dina that way to keep the exact sequence intact so his friends could ultimately stop him and survive. It wasn’t that he “wanted” Carla dead out of malice; it was that he had already locked himself into a future where her death was the necessary fuel for his rage, the Rumbling, and the only outcome where Paradis and his friends weren’t wiped out. He traded his own mother’s life for a future he had already glimpsed and refused to abandon, even knowing it would break him. That’s the full weight of the Founding Titan and Attack Titan’s power working together—Eren wasn’t just following fate; he was actively writing the past to preserve the only ending he could live with.

The main reason Eren couldn’t start the Rumbling when he kissed Historia’s hand is that the Founding Titan’s full power only activates through contact with a Titan of royal blood, not a regular human. Historia has royal blood, so touching her let Eren access the Paths and see both Grisha’s memories and fragments of his own future (including the Rumbling), but she wasn’t in Titan form. That’s why the Walls stayed sealed—he only unlocked memory transfer, not the ability to command the Colossal Titans inside them. He later meets the actual requirement when he touches Zeke, a royal-blooded Titan shifter, which finally lets him fully awaken the Founder and begin the Rumbling. At the ceremony, Eren was also still processing the horrific future he’d just glimpsed and wasn’t yet ready (or positioned) to force that outcome, even if the mechanical conditions had somehow been met.

Titan shifters can actively control or delay their regeneration through will and focus, not just by lacking the desire to live. Eren had refined this control by the time of his Marley infiltration (as confirmed in the series and supporting materials), similar to how Reiner suppressed the healing of his severed arm until he chose to reveal himself as the Armored Titan. He deliberately cut off his own leg and gouged out his eye to sell the cover of a traumatized Eldian war veteran, then restrained the healing process for the duration of his hospital stay and undercover work. This wasn’t passive non-healing—it was deliberate suppression of his Titan powers so he could blend in among the wounded soldiers, gather information, and coordinate with allies without drawing suspicion. Once the disguise was no longer needed (such as when confronting Reiner), he regenerated the injuries on command, proving the restraint was temporary and fully under his control.

Eren clocking that transformation flash and immediately treating it like an opening instead of a free cutscene is peak “I’ve been in enough of these to know the rules don’t apply to me anymore” energy. Most characters in these situations still pause like the animation budget is sacred and they’re not allowed to move until the music swells, but he just sees the vulnerability window and takes it. That kind of fight IQ is what separates the ones who keep getting surprised by the same tricks from the ones who start dictating how the fight actually goes. It also makes the earlier seasons’ more straightforward brawls feel almost quaint in retrospect. Once Eren stops respecting the theatrical timing of enemy power-ups, the whole dynamic shifts—he’s no longer reacting to whatever the other side wants to set up, he’s forcing them to complete their transformation under active pressure. That’s not just aggression; it’s him reading the meta of the world he’s in and refusing to play along with it.

Historia wasn’t forced into the marriage or pregnancy—it was her own calculated choice to buy time. The Paradis military (following the partial plan from Zeke and Yelena) intended for her to inherit the Beast Titan as soon as Zeke arrived so she could start producing royal-blooded children and keep the Titan powers in the family. By getting pregnant first, she made it impossible for them to turn her into a Titan without killing the baby, which delayed the whole process by roughly nine months and gave Eren (and the others) room to maneuver. The farmer wasn’t some random duty assignment either; he was a childhood acquaintance who used to throw rocks at her, later worked at her orphanage to make amends, and ended up as the confirmed father. The military even background-checked him and Nile Dok emphasized that starting the relationship was Historia’s decision. After everything, they do marry, though the series leaves the exact balance of love versus practicality a bit vague. The whole subplot is messy and undercuts some of her earlier “live for myself” development, which is why a lot of fans still find it frustrating, but within the story it’s framed as her exercising what little agency she had left rather than pure coercion. The popular “Eren is the father” theory got debunked by the manga and anime both confirming the farmer.