A Dream I Once Had

 is the 70th chapter of the Attack on Titan manga, written and illustrated by Hajime Isayama.

Overview
Two months after Historia's crowning, the Survey Corps now rule over the Walls with the monarchy just acting as a display. Historia opened an orphanage using the properties confiscated to the nobles for all orphans within the Walls. Eren has mastered his Titan hardening abilities and the Survey Corps are preparing a strategy to confront Reiner and Bertolt in case they return. All members of the old government have been arrested and their allies obliged to pay high taxes; their technology was confiscated and the shining Titan stones found in the Reiss chapel were given to the citizens as an infinite source of light. Hange develops a guillotine-like weapon made with Eren's Titan stone capable to kill Titans without need to fight them, though at great cost for Eren's health. The Survey Corps prepare a plan to retake Wall Maria using this new weapon. Hange reveals the results of the studies made to the Titan serum and its care is trusted to Levi. Marlo and some other members of the Military Police join the Survey Corps. Eren recalls some memories of Grisha encountering Keith Shadis after the massacre in the Reiss chapel and plans to meet with him and ask him what he knows about it. In Shiganshina District, Reiner is defeated by the Beast Titan. The human inside it emerges and orders him and Bertolt to wait for the Survey Corps so the three can ambush them when they come.

Summary
As Historia Reiss is crowned queen, Erwin Smith recalls before their battle with Rod Reiss, when she asked him to tell the citizens that she was the one to kill Rod. He then silently states his surprise at the fact that she actually did kill Rod.

Two months after being crowned, the Survey Corps has taken over the thrown, with Historia allowing them to rule in her stead so that she can run an orphanage for children who were orphaned during Titan attacks, and children living in the Underground City. After the Survey Corps took power, the former Councilors and their staff had their titles stripped, and were sent to prison camps to pay for endangering humanity's future for their own selfish desires, and any nobles left were forced to pay taxes to the new government (with those who opposed it being forced to pay more than those who cooperated with it). Numerous technological advances have also been made thanks to the equipment left over by the Military Police Brigade, and the shining rocks from Rod Reiss's underground cave have been provided to the civilians as a light source that doesn't require energy.

Between helping out at the farm that serves as Historia's orphanage, Eren Yeager has been steadily mastering his hardening abilities thanks to training with Hange Zoë. In the past two months, Eren has used his hardening ability to reinforce the hole in Trost District, as well as form a scaffold in the wall to catch any Titans that attempt to enter. Hange has also designed a battering ram on top of the wall to execute the Titans caught in the scaffold to execute the Titans without risking the lives of soldiers by directly engaging them. Hange is thrilled to see that the ram is able to execute the Titans, but is surprised to see that Eren's nose has begun bleeding. Levi suggests that Eren's training has taken a toll on his body, and that he should slow down, but Eren insists that they must continue preparing for their expedition to Shiganshina District.

Later, Erwin, Levi, and Hange participate in a meeting with Darius Zackly, Dot Pixis, and other military higher-ups to inform them of their progress and preparations. Erwin informs them that the Survey Corps' night expeditions to clear a path to Shiganshina have been going well thanks to the rocks from Rod Reiss' underground caves, and that the Corps should be ready to leave for Shiganshina within a month. One of the officials is surprised by how quick the Survey Corps is moving, and reminds Erwin that if their next expedition fails, the Military will be left bankrupt. Erwin assures him that the Corps is willing to do everything on its power to ensure that all of their comrades' sacrifice will not have been in vain.

After the meeting, Pixis attends a private meeting with Erwin, Levi, Hange, and Zackly to discuss the syringe given to Levi by Kenny Ackerman. Hange reports that all efforts to analyze the syringe and its contents have failed due to their lack of the technology necessary. Hange reports that although the contents of the syringe appear to be fluid from a human spinal cord, it vaporizes upon contact with air and so cannot be further researched. Without being able to research it, it is decided that the syringe, and the decision as to whether it should ever be used will be entrusted to Levi.

Recently, members of the Garrison and the Military Police Brigade have begun to transfer to the Survey Corps to boost it dwindling ranks. Among those who have transferred is Marlo Freudenberg, who is ecstatic over Hange's new Titan-executing ram, claiming that using it, mankind will finally be able to wipe out the Titans. Jean Kirstein is less than convinced, claiming that its hard to believe someone like Marlo who has never seen a Titan. Marlo is undeterred, claiming that he is not the only member of the Corps to be excited over Hange's invention, but Jean points out that only those who have recently transferred, like Marlo, are excited. This attracts the attention of some former 104th Trainees Squad members who have recently transferred from the Garrison. They claim that they are not the only ones excited, and that everyone is ready to take back Wall Maria. When Jean brushes them off, they question what happened to him and the others to leave them the way they are, but leave when they don't get an answer. Marlo notes that he had been acting like them, embarrassed, prompting Sasha to ask him why Hitch Dreyse didn't try to stop him. Marlo notes that Hitch stayed with the Military Police and tried to convince him to stay for the benefits they would be given for helping overthrow the government, but that he had refused, claiming he had been wrong about her. Eren is the only person who isn't appalled at him, claiming that what he said was true.

Connie Springer decides to leave early so that he can prepare for his trip to Ragako Village. After he leaves, Sasha wonders if they will be able to change the Village inhabitants back to human form, prompting Eren to recall when he learned that Titans were really humans, and notes that he there have been times when he became a mindless Titan, but that he cannot remember anything of it, only knowing what his father Grisha saw. Jean suggests that Eren try to remember the man he saw in Grisha's memories, to which Eren agrees, concluding that the man from Grisha's memories must have known something. Eren notes that the man looked familiar, but that he could not remember where he had seen him before. Jean's suggestion that he have their old drill instructor Keith Shadis head-butt the memory back into him leads Eren to the realization that it was Keith his father encountered in the memory, and declares that he will visit Keith in the morning.

In Shiganshina, Bertolt Hoover watches in horror as the Beast Titan stands triumphant over Reiner Braun's battered Titan form. As Bertolt pulls Reiner from his Titan, the Beast Titan declares himself victorious, and that the rescue of Annie Leonhart will have wait, as acquiring the Coordinate is their first priority. As a man emerges from the Beast Titan and dons a pair of spectacles, he declares that if they wait, Eren will come to them.