|We're conscripts. Natives of lands that Marley invaded who were drafted. We were sure we'd never have a chance to oppose them. Until...we met him...|
|— Yelena to Hange Zoë and Levi Ackerman|
The members of the Anti-Marleyan Volunteers seem to possess a severe grudge against Marley, in part because of the empire's aggressive policy of expansion and the take over of their native lands. Before their introduction to Zeke Yeager, the volunteers generally had low morale due to the adversity in opposing such a powerful nation. However, after meeting Zeke the soldiers became more hopeful. The Anti-Marleyan Volunteers hold a strong devotion towards their leader, with Yelena even comparing him to a God.
The Anti-Marleyan Volunteers started off as a loose collection of rebels organized by Yelena. The members largely composed of people from different nationalities that had seen their homeland being conquered by Marley. After being forced afterwards to join the Marleyan forces and to fight for the country that oppressed them, they grouped together to try to take down Marley and secure their freedom.
As stated by Yelena, they initially had very little success and lost morale over time. After meeting Zeke Yeager, their spirits were renewed, and the two sides joined forces. Furthermore, the volunteers originally found it difficult to mesh together with all the uncertainty amidst. However, Yelena's ruthless murders of doubtful Marleyan comrades reduced this by lowering conflict, with members seeing this as a necessary evil.
During the early stages of the Marley Mid-East War, the Anti-Marleyan Volunteers betray the first survey fleet sent to Paradis Island, and make contact with the Eldians living there. In their leader's stead, they make a deal to help the Survey Corps with covert diplomacy, technological transfer, and intelligence gathering in exchange for granting Zeke and his followers amnesty on the Island.
The Anti-Marleyan Volunteers would continue to aid the Survey Corps playing a crucial role in the Raid on Liberio. Yelena would infiltrate the Marleyan ranks to incapacitate two of Marley's Warriors while Onyankopon and others would pilot an airship to ensure the Survey Corps can escape.
After returning to Paradis, the Volunteers turn over a stock of Titan serums they managed to steal from Marley to the Garrison. After receiving the serums, Dot Pixis has his soldiers arrest the Volunteers at gunpoint; apologizing for their rough treatment but asserting that Paradis is not yet willing to trust Zeke and his followers completely.
After Dot Pixis surrenders to the Yeagerists, the Volunteers are released from house arrest. They then join Yelena and Pixis in the Shiganshina District where Yelena ostracizes the commander for provoking Zeke Yeager.
In the aftermath of Marley's attack on Shiganshina, Floch Forster immediately orders the arrests of all the Volunteers. Once they are gathered, Floch begins to ostracize the group by wounding one who refused to show proper respect while reminding the rest of them about the loss of their leader and the imminent destruction of their homelands. Floch then extends an offer to spare those who will lend their strength for the sake of the Eldian Empire before executing the wounded Volunteer who continued to speak out in defiance. The Volunteers can only watch their comrade's corpse with anguish as they are escorted to their cells to consider the offer.
Afterwards, Yelena is branded as a criminal for her actions along with Onyankopon who refused to continue serving the Eldian Empire. Before their execution, they are saved by the Cart Titan and brought to Magath who formed an alliance with Hange and other members of the Survey Corps. After the Rumbling is triggered by Eren Yeager, the Volunteers assist the ragtag group by helping the Hizuru engineers prepare a flying boat to get ahead of the Wall Titans scouring through Marley.