The Stohess District raid (ストヘス区急襲 Sutohesu-ku kyūshū?) was a conflict between the Survey Corps and the Female Titan within Stohess District, the eastern city of Wall Sheena, in which the Female Titan was captured and the existence of Titans within the Wall was discovered.
During the 57th Expedition Outside the Walls, Armin Arlert encountered Annie Leonhart, the Female Titan, and was able to deduce her identity after considering her actions during the expedition and seeing her Titan's face up close. After the Survey Corps' return to Karanes District, he shared this deduction with Commander Erwin Smith, who devised a plan to capture Annie in Stohess District, Annie's base of operations in the Military Police Brigade and the half-way point between Karanes and Mitras where the Survey Corps had been summoned to hand Eren Yeager over to the MPs. This plan was shared with Eren, Mikasa, and Captain Levi first, though Eren was in great disbelief and denial at the possibility that Annie was the Female Titan.
While a majority of the Survey Corps made their way from Karanes to Stohess on their way to the capital, a squad headed by Mike Zacharias supervised a group of new Survey Corps recruits, leading them to an isolated base in Wall Rose where they would be under close watch. This was done to isolate Annie from any potential accomplices who could aid her during the Stohess District raid.
Annie Leonhart, having returned to Stohess District after her failure to capture Eren Yeager, began to oversleep in the days to come due to the great stress brought on by her prolonged time spent in multiple Titan forms.
On the morning of the raid, the new recruits of the Military Police Brigade, including Annie Leonhart, were assigned with escorting the Survey Corps through Stohess District on their way to Mitras. As Annie joined her comrades on their way to the escort mission, she was beckoned aside by Armin who informed her of a plan by the Survey Corps to sneak Eren out of the district. After some convincing, Annie agreed to help Armin and the others. Suspecting a trap, Annie equipped herself with a blade-ring in order to trigger a Titan transformation if necessary.
With Eren and Mikasa, the four made their way to the entrance of a tunnel of an abandoned underground city which would lead them to the outer gate of Stohess. In reality, the tunnel was chosen to restrict Annie's ability to transform into a Titan and Survey Corps soldiers would await them below to capture her. Meanwhile, various members of the Survey Corps in civilian disguises waited out of sight in the event that the first plan failed. Annie hesitated to follow them underground, and the others questioned her choice with as little suspicion as possible. However, their conversation quickly became heated as Annie realized she was cornered, no longer denying her identity as a Titan. Mikasa became impatient and prepared to strike as Annie readied herself for Titan transformation, but Armin fired a signal flare to alert the disguised soldiers of the plan's failure. The soldiers quickly rushed Annie and restrained her, but Annie successfully slashed her thumb with her blade-ring and transformed, killing the soldiers around her as Eren, Mikasa, and Armin fled into the tunnel.
The three recruits attempted to meet up with the soldiers in the tunnel to initiate their plan B, but Annie's Female Titan stomped a hole into the tunnel, killing the team before any action could be taken. Eren proposed transforming into a Titan in order to shield himself and his friends from Annie, but his internal denial about Annie's betrayal prevented him from transforming. Armin proposed that he and Mikasa would split up and leave the tunnel from both the entrance and the hole left by Annie's foot at the same time, dividing her attention in order for Eren to safely escape. Eren wondered at his friends' ability to accept Annie's betrayal, and Mikasa simply attributed it to the cruelty of the world. Eren accepted this and found the strength to transform, engaging in battle once again with the Female Titan.
In his Titan form, Eren engaged in combat with Annie in the streets of Stohess District. Upon hearing the Titans' brawl elsewhere in the city, the Survey Corps' escort came to a halt as Commander Nile Dok sent his recruits to investigate. Commander Erwin Smith advised him to dispatch all available Military Police officers, and the escort to Mitras ceased.
The fight between Annie and Eren continued as the two caused significant damage to the structures of Stohess, including a church where Minister Nick was giving a sermon to his followers of the Church of the Walls. Annie eventually disengaged and attempted to reach Wall Sheena and escape, but her brawl with Eren continued for a short while before Eren was briefly incapacitated. By the time Eren was back on his feet, Annie had begun to scale Wall Sheena using her hardening ability to dig her fingers into the stone. Before Annie could reach the top of the Wall, Eren managed to throw Mikasa up to Annie's position where she sliced the Female Titan's fingers. Annie fell to the ground below and was quickly surrounded by Survey Corps personnel, who immediately began to extract her from her nape. Once she was exposed in her Titan's nape, Annie made a last-resort move and encased her body in impenetrable crystal with her hardening powers, preventing her interrogation while resigning herself to capture.
By the end of the battle, over one hundred civilians had been killed or wounded in the fight between Eren and Annie. The Survey Corps made quick efforts to relocate Annie's crystal underground to prevent future Titan transformations. At the same time, the Survey Corps soldiers present spotted a gap in Wall Sheena where the Female Titan had damaged the stone, revealing the face of a Colossus Titan within. Minister Nick quickly arrived at the scene and urged Squad Leader Hange Zoë to cover the Wall Titan to prevent the sunlight from touching it. Hange's team gathered necessary supplies to cover the hole in the Wall while Military Police Brigade recruits demanded answers concerning the day's events, though all information was kept confidential at the moment.
Once the Wall Titan had been successfully covered, Hange interrogated Minister Nick concerning his knowledge of the Wall Titan. Despite threats against his life, Nick refused to reveal any information.
Later that afternoon, leaders of the Survey Corps were summoned to the Military Police Brigade Stohess branch headquarters to answer for the events of that day. Erwin Smith stated that information concerning the mission was kept hidden from the Military Police due to the possibility of accomplices of Annie Leonhart acting within the brigade. Annie was confirmed to be detailed underground, out of commission despite the impossibility of interrogating her for information. However, before the meeting could conclude, Survey Corps soldier Thomas arrived at the meeting to warn the Survey Corps leaders of a Wall Rose invasion that had been occurring at the time of the Stohess District mission. The members of the Survey Corps present in Stohess District immediately assembled and made their way southwest to Ehrmich District to assist in the evacuation of Wall Rose.