|I suspect their only purpose now is to put Zeke and Eren in contact with one another. Then, they'll remake the military with Eren at the top.|
|— Hange theorizes on the Yeagerists' plan|
The Yeagerists (イェーガー派 Yēgā-ha?) are a rebel faction supported by civilians and former soldiers from the Paradis military. Their goal was initially to reunite Eren Yeager with his half-brother Zeke, and to create the "New Eldian Empire" (新生エルディア帝国 Shinsei Erudia Teikoku?), and ultimately assist the former in the activation of the Rumbling. By the year 857, Eldia's military would be controlled by the Yeagerists.
The Yeagerists believe Eldia is on the verge of destruction and only they can save the island by dedicating themselves to Eren Yeager. The rebellious faction claims those who subordinate themselves to the outdated ideals of the current Royal Government will only watch as they are devastated by the outside world.
Initially, the group was known to consist of over a hundred members, many of them from the Survey Corps. However, the true extent of their influence is unknown with many soldiers and civilians vowing to devote their hearts to Eren Yeager. Around 500 soldiers connected with the Yeagerists are present in Shiganshina District at the time of Marley's invasion. It is said the Yeagerists effectively control everything inside the Walls.
The initial formation of the Yeagerists was around the time Eren informed Floch Forster about his intentions to use Zeke Yeager to grasp the power of the Founding Titan. Afterwards, Floch began gathering comrades in secret to help Eren with his plan. Later on, Eren would begin to act on his own while defying the military that intended to feed Zeke Yeager to Historia Reiss upon his arrival to Paradis.
After Eren's infiltration of Marley and the resulting Raid on Liberio, he was arrested for his actions which resulted in the deaths of several Survey Corps soldiers. Word starts to spread about his imprisonment and the ones who leaked the story are arrested as well. Meanwhile, protesters start to gather and demanding that Eren be released from his confinement.
At some point, more people began to reveal that they see Eren Yeager as their savior who could save the Eldian Empire.
Meanwhile, Yeagerists within the Survey Corps would begin covertly working with Zeke's trusted follower Yelena and procure wine for the soldiers detaining Zeke within the Titan Forest. This wine was taken off the captured Marleyan ships and is tainted with Zeke's spinal fluid; it was also instructed to be given out to many senior heads of the Military to neutralize them as possible threats.
Eventually, several members plant a bomb in a chair belonging to Commander Darius Zackly and place it in his office. They later trigger the bomb, killing Zackly and several members of the Military Police. At roughly the same time, Eren uses his newly granted powers of the War Hammer Titan to tunnel his way out of his cell and seals his escape route so he could not be followed. While this happens, the other members free Eren's allies and escape the prison as well. Regrouping out in the mountains, Eren meets with his followers and declares he will locate Zeke.
After Eren's escape, the top military officials meet with Dot Pixis who believes the Yeagerists will target anyone who knows where Zeke is being held and then capture Queen Historia, who could act as a replacement for Zeke. Pixis then declares they will negotiate with Eren using Zeke's location and grudgingly decides to disregard their assassination of Darius Zackly in order to avoid more deaths, stating it is a cheap price to pay. However, this is just a ruse of the commander to abduct their leader and steal the Founding Titan from him. The Yeagerists would somehow receive word of the proposal, but it is rejected by Eren who refuses to entrust Commander Pixis with the fate of the island.
The Yeagerists later storm into a restaurant to attain the location of Zeke Yeager from Hange after receiving word from a Marleyan. The Yeagerists then capture those present at the restaurant including several officers of the Survey Corps and the Blouse family before departing to the Shiganshina District.
While in Shiganshina District, the Yeagerists interrupt a 109th Training Corps exercise in an attempt to seize control of the division. Floch is able to quickly drum up support from the sympathetic trainees, and rebuffs Keith Shadis, who he has the trainees beat to prove their loyalty to the Yeagerist cause. After praising the Yeagerist affiliated division, Floch once again demands that Hange take them to Zeke's location.
En route to where Zeke was being held, Floch and the Yeagerists accompanying Hange hear a loud rumble and wonder what it could be; following the sound, they discover a demolished wagon with a small Titan nearby. After Hange discovers the body of Levi Ackerman, the Yeagerists become startled when the Titan begins emitting steam and a fully healed Zeke Yeager emerges from the Titan's stomach; Hange then escapes with Levi's body, causing several Yeagerists to chase after them. At the same time in Shiganshina, Eren goes to the prison cell where a captive Gabi is kept, only to be ambushed by Pieck, a Warrior from Marley who infiltrated the Yeagerists.
Many armed soldiers join Yelena and Eren on the roof of the jail when Pieck supposedly prepares to divulge the location of Marleyan spies. Galliard, who had also been posing as a Yeagerist, transforms inside the compound and begins a battle with Eren. Concurrently, several airships fly over the district, parachuting in Marleyan soldiers who take the upper hand in a firefight with the Yeagerist forces.
As the Yeagerists scramble to fight the forces from Marley, the Beast Titan arrives and begins destroying the airships from atop Wall Maria. Eventually, the imprisoned Survey Corps soldiers are released and head towards the other imprisoned Eldians; after a brief scuffle, the others are freed as well and the two groups reluctantly join forces to fight Marley.
As the conflict continues, a squad of Yeagerists ambush the Cart Titan. After the Titan is seemingly defeated, Floch remains skeptical but is caught off guard and forced to retreat with the other Yeagerists when Marleyan soldiers open fire from the Cart Titan's carcass. Aside from Floch, all of the Yeagerists in the group are killed in the attack.
In the aftermath of Eren beginning the Rumbling, the Yeagerists join their former prisoners in killing the Titans that Zeke had created in the battle. After all the Titans are eradicated, Floch joins the survivors at the military headquarters, and orders the Anti-Marleyan Volunteers be gathered and restrained. Once they are present, Floch issues the volunteers an ultimatum. He offers to accept them as Eldians if they agree to cooperate with the Eldian Empire, though disagreeing would have them face execution.
In the following days, the Yeagerists gather to proclaim the end of Eldia's persecution from the outside world, and begin celebrations. Later at the military HQ, a group of Yeagerists gather to witness the execution of Onyankopon and Yelena, who refuse to side with the Empire. Before the executions can be carried out, the Cart Titan suddenly attacks, eating Jean and the two volunteers. The Yeagerists attempt to follow them, but are unsuccessful.
Anticipating that Jean and his allies will try to use Kiyomi Azumabito's flying boat to reach Eren, Floch mobilizes a group of heavily armed Yeagerists to occupy Paradis's harbor. They are able to get there quickly by the use of steam engine and take Kiyomi hostage.
Following an attempt by Armin and Connie to get to the flying boat, Floch decides to execute the Azumabito mechanics to keep them from posing a threat in the future. However, he is caught off guard and disarmed by Kiyomi. Before Floch's comrades can help him, Mikasa bursts into the building and incapacitates them as well. With no one to help, Floch flees the building and alerts the rest of the Yeagerists that they are under attack. The Yeagerists fire Thunder Spears into the building, before being caught off guard by the appearance of the Armored and Female Titans.
The Yeagerists desperately attempt to kill the two Titans along with the fleeing Azumabito service crew but many are swiftly slain by their former allies from the Survey Corps. As the situation becomes dire, Floch deduces that their adversaries will escape using the Azumabito's ship and rallies the Yeagerists to stop them. The Yeagersits are soon unable to accomplish their objectives due to the arrival of the Cart and Jaw Titans along with the sudden loss of their reinforcements. However, Floch is still able to target the ship but falls into the ocean after being shot by Gabi. As the Azumbaito's ship departs, the remaining Yeagerists pursue a Marleyan and another Paradis soldier into a cruiser which self destructs shortly after.
Determined to stop his opponents, Floch latches on to the fleeing ship and pursues them all the way to Odiha where he sneaks into a hanger and opens fire upon the flying boat. Despite his efforts, Floch is swiftly slain and with his dying breath he begs his former comrades not to stop Eren.
Over the years since Eren's death, the Yeagerists continued to grow in size; by the year 857, they eventually reached the point where they formed a new army in order to protect Paradis Island from any and all future threats.