The Anti-Marleyan Volunteers
In 851, Zeke Yeager sent Yelena and Onyankopon of the Anti-Marleyan Volunteers on an infiltration mission. They integrated themselves as part of the crew of a Marleyan ship that went to Paradis. When the ship was captured by the Survey Corps, Yelena killed the captain and agreed to Commander Hange Zoë's suggestion to talk. The two soldiers then shared their knowledge and technology with the Survey Corps.
All three branches of the Paradis military met and discussed Zeke's stipulations to earn his cooperation. Eren explained that Zeke had figured out how they can use the Founding Titan without being controlled by the vow to renounce war, since Eren could activate the Founding Titan without being a descendant of the Fritz family as long as he was in contact with a Titan of royal blood. On hearing that, Hange decided to work with the Anti-Marleyan Volunteers.
With their help, the Survey Corps captured the other survey ships Marley sent to Paradis and were able to commandeer them for trade with other nations across the sea. Over time, the Survey Corps was able to befriend some of the captured Marleyans and their engineers were able to assist Paradis' rapid growth in technology in preparation for taking the battle to Marley.
Nations in decline
Three years later in 854, the Armored Titan suffered an unceremonious near-defeat at the hands of the Mid-East Allied Forces' anti-Titan artillery, serving as a grim reminder to the Marley military that the era of the Titans was coming to an end. Following Marley's victory over the Allies, the leaders of the Marleyan military gathered to discuss the apparent threat to their global influence. Commander Theo Magath, noting the Allies' superior navy in the recent war, was of the opinion that reliance on the power of the Titans could not guarantee victory in ground-based warfare any longer, especially given the rising advent of military aircraft which would render the Titans completely obsolete in battle.
Feigning loyalty to Marley, Zeke proposed the plan to focus Marley's efforts on taking the Founding Titan in order to gain an advantage in Titan-based warfare while simultaneously making efforts to improve conventional weaponry. Since his term as the Beast Titan had approached its final year, Zeke desired to complete this objective himself in the short time he had left to live before passing his power on to Warrior candidate Colt Grice. This proposition appeased General Calvi, who assured Zeke that his plan would be passed on to the governmental party of Marley. However, there were other matters on Zeke's mind related to the imminent end of the Titan era.
Upon returning to Liberio, Zeke gathered the Warriors together to discuss the fate of the Eldian race. Given the declining practicality of Titan weaponry, this decline would inevitably apply to the Eldians who served as the basis for the Titan power. Once the Titans outlived their use, the continuing existence and guaranteed safety of the Eldian race would be at great risk in Marley and the world at large.
The Tybur family, a family of Eldian aristocrats in Marley and the keepers of the War Hammer Titan, would resolve this threat by acting as the spokespeople for both Eldia and Marley. During an upcoming festival being held in Liberio, journalists and ambassadors from around the world would gather to hear the words of the Tybur family, who would mark Paradis Island as the greatest threat to world peace and would guarantee the island's fall within a year. With this strategy, the security of the Eldian race and Marley's continued dominance over the world would be guaranteed.
A new Helos
Soon afterward, the Tybur family arrived in Liberio where Commander Magath met with Willy Tybur, the head of the family. Together the two discussed the declining state of their nation, comparable to the empty legend of Helos the slayer of the Devil, and the suffering of the Eldian people, both crises which the Tybur family were in some way responsible for.
As Magath had suspected, the Tybur family had been acting as the true ruling head of Marley, though in matters of both Marley's military policies and the subjugation of the Eldians the Tyburs remained uninvolved observers. Wishing to right these wrongs, an alliance was struck between Commander Theo Magath and Lord Willy Tybur to save Marley and Eldia from destruction.
Throughout the next month, as preparations for the grand Liberio festival were underway, Tybur and Magath began conspiring against the top brass of the Marleyan military, the greatest threat to Marley's advancement and the peace of the Eldians. By Magath's investigations, the leaders of the Marleyan military had become "aged" like the structure of a poorly-tended home requiring large-scale demolition. Given this necessity, Commander Magath was placed in a position that would make him the general of Marley's military forces should the need arise. However, despite the military's needed demolitions, some of the structure's "posts" were still usable and had informed him of rats that had infiltrated the home.
At some point during the Marley Mid-East War, Eren Yeager had infiltrated Commander Magath's Eldian Unit disguised as a soldier named "Kruger," presumably acting on his own decisions rather than under orders from his superiors. In the initial days after the war, Eren kept a close watch on the Warriors, particularly Reiner Braun, and began to take pity on the Eldians for the subjugation they faced on the mainland.
After returning to Liberio, Eren faked psychological trauma and was sent to recover with other damaged soldiers in a hospital. At this hospital, Eren met Warrior cadet Falco Grice, who became his close acquaintance. Claiming to send correspondence to his family, Eren used Falco as a means to deliver messages to his allies in the Survey Corps who were searching for him. This correspondence would continue over the course of the next month leading up to the Liberio festival.
While the details of the infiltration were muddled, Commander Magath and Willy were well aware of the spies lurking in their homeland. Given the knowledge that 32 scout ships sent to Paradis Island had disappeared in the past three years, it was suspected that the forces of Paradis Island were at work.
Sensing an opportunity for Magath's rise to power, Willy suggested clustering the undesirable authorities of the Marleyan military together during the upcoming production to serve as bait for whatever attackers may come forth. The party of Marley would grant Magath full authority to select any officers he desired to be the authority in his newly rebuilt military.
Magath was wary of the plan, noting that many innocents would die and Willy's life would be at great risk as well should the festival production come under attack. These would be necessary losses in Willy's eyes, who believed the world would not take his side if he escaped any disaster alone. With the bait set, the festival was ready to proceed.
The curtain rises
On the night of the Liberio festival, the preparations made between Magath and Lord Tybur were underway. As planned, General Calvi and the leadership of the Marleyan military were clustered together near to the stage while ambassadors and journalists from across the world were gathered to witness the stage production planned by Willy. From the rooftops, Commander Magath oversaw the stage production while receiving news of suspicious activity from his subordinates. Anti-Titan artillery was also placed on the rooftops.
At this time the Survey Corps began to act from the shadows against Marley, sending a spy to trap Porco Galliard and Pieck, the Jaw Titan and Cart Titan respectively, away from the site of the production. This same spy sent Zeke Yeager away from the festival area, though Zeke was not taken away with Pieck and Galliard. Suspecting ill intent, Pieck informed her Panzer Unit of the soldier's strange behavior, telling them to follow her. After being led indoors, the spy trapped Pieck and Galliard in a deep pit where they could not transform into their Titans. News of their disappearances soon reached Magath, who mobilized the reserve troops.
Elsewhere, Eren requested for Falco to lead Reiner Braun to him in a basement room behind the Liberio stage, leaving the audience devoid of any Warrior Titans. Shocked to see Eren in his hometown after four years, Reiner cautiously listened to Eren's threat of transforming in the basement and murdering the civilians in the building above listening to the production. At this time, Willy's stage production began.
Recounting the atrocities of the ancient Eldian Empire, Willy reminded his audience of the horrors brought by the Titans and Marley's triumphant victory over the Eldians in the Great Titan War a hundred years ago. However, Willy used this opportunity to reveal the truth of the Great Titan War which he learned upon inheriting leadership of the Tybur family: Eldia's downfall came from within at the hands of King Karl Fritz who conspired with the Tybur family to destroy Eldia and place Marley in power.
With the truth of Eldia's downfall made public, Willy declared Paradis Island to be the greatest threat to peace in the world: the Founding Titan that had guaranteed the pacifism of the Walled Kings was now in the hands of Eren Yeager, who could use the Founding Titan through methods unknown to Marley. In this desperate time, Willy called for the union of the world's armies to end the threat of Paradis Island and usher in a new age of peace. Finally understanding who his true enemies were, Eren reveals that he saw himself in Reiner and took pity on him. Taking Reiner's hand, Eren committed to continuing his advance until his enemies were destroyed.
With the eyes of the world on him, Willy Tybur denounced the devils of Paradis Island and made a declaration of war. At the same time, the Attack Titan burst forth from behind the stage and destroyed it, killing Willy and eating him. Chaos erupted in the audience as debris fell from above, crushing many to death. Seeing the Marley military officials seated nearby, the Attack Titan lunged into the stands, killing General Calvi and many other high ranked members of the Marley military. As the survivors in the audience fled for their lives, the younger sister of Willy emerged from the ruined stage to transform into the War Hammer Titan, though her Titan was quickly intercepted and beaten into the ground by the Attack Titan.
Commander Magath took charge of the situation, ordering for his men to report to their battle stations as the War Hammer Titan gained the upper hand by impaling the Attack Titan on a massive spike. While the Titans dueled, Pieck and Galliard were rescued by the Panzer Unit and prepared to equip the Cart Titan for battle. At this time, the Warriors noticed enemy soldiers flying overhead on vertical maneuvering equipment. The Attack Titan struggled to evade the War Hammer's strikes and the barrage of artillery fire.
Koslow worried over the possibility of losing the Founding Titan, though Magath insisted that ridding Paradis Island of the Founder would be more beneficial than Marley attempting to gain it. The Attack Titan was quickly caught and defeated by the War Hammer Titan, who prepared to kill Eren Yeager after he was forced to emerge from his Titan's nape. When asked for his final words, Eren called for Mikasa Ackerman to strike at the War Hammer from behind. Using a barrage of Thunder Spears, Mikasa felled the War Hammer before reuniting with Eren while the soldiers of the Survey Corps engaged in a firefight with Magath's troops. Despite the heavy damage done to the nape, the War Hammer Titan regenerated its body and retaliated, forcing Eren and Mikasa to abandon the Attack Titan. Mikasa continued to attack the War Hammer while Eren formulated a new strategy.
Commander Magath's troops relocated to an abandoned building where Magath called for backup from the 30,000 troops stationed to the east and west of Liberio (the division of the army under vigilance training on the mountain and the offshore fleet). Meanwhile, the arriving Survey Corps continued their assault on the Marley military, killing rooftop soldiers and bombing Magath's troops in their hideout. Floch Forster began incinerating entire buildings in the process, to the dismay of his comrade Jean Kirstein. While civilians evacuated the internment zone, the Survey Corps soldiers killed any inbound Marleyan troops, leaving small lights on top of cleared buildings.
Once the area was clear, the Survey Corps soldiers regrouped at the plaza with Eren and Mikasa, joined by Levi Ackerman. Commander Magath and his troops made their way to the plaza as well, along with Warrior Cadet Gabi Braun who had survived the outer firefights. Discovering the War Hammer's ability to remotely control the Titan, Eren discovered the crystal underground holding the younger sister of Willy, severing its connection to her Titan and preparing to eat it with his Attack Titan. At this time, Galliard's Jaw Titan arrived at the scene, attempting to eat Eren Yeager and the Founding Titan. Levi cut at the jaw muscles of the Titan, preventing it from biting through, just as Pieck's fully-equipped Cart Titan and Zeke's Beast Titan arrived at the scene. Having regenerated its connection to the ground, the War Hammer Titan generated a tree-like structure impaling the Attack Titan. The Titans regrouped in the plaza, ready to annihilate the invading Survey Corps.
As the two sides engaged, Mikasa fired a Thunder Spear at the crystal around the younger sister of Willy, but failed to shatter it. Eren also tried biting the crystal with his Titan's teeth, but only managed to shatter his own jaw. Meanwhile, Pieck and her Panzer Unit provided covering fire for Zeke's Beast Titan, and the Marleyan forces began to get a feel for how the Survey Corps moved in combat. This allowed Galliard to kill an opposing soldier who was closing in on Pieck. However, in the heat of battle, the Warriors lost track of Levi.
Despite Eren abandoning the trapped body of his Titan and reforming a new one, the battle swayed in the Warriors' favor. The Survey Corps soldiers were forced to take shelter inside buildings and they did not bring much in the way of weapons or fuel with them. This allowed the Warriors to be cautious with their moves, because they knew they had little chance of losing.
Falco Grice found Magath by the building protected by the Beast Titan and claimed that Reiner was stuck in the ground, unable to move. Gabi joined them as Falco explained that Eren Yeager was the one who had trapped Reiner.
Second attack wave
Out in the nearby harbor, the recalled Marleyan navy discovered a small fishing vessel with a single cloaked figure in it. Armin transformed into the Colossus Titan and caused an explosion that devastated the navy and the surrounding area, with the resulting blast being seen and felt as far inland as the internment zone.
Outraged by Paradis Island using Bertolt Hoover's Titan power, Galliard charged at Eren, believing that he could force an end to his enemies' plans if Eren was dealt with. However, he was met by Mikasa Ackerman as part of the Survey Corps' renewed offensive. As Mikasa faced Galliard, Levi made a surprise attack on the nape of the Beast Titan. He felled the Beast Titan in front of a shocked Magath, Gabi, and Falco, and dropped a bomb into the open wound, appearing to kill Zeke. The Cart Titan had its Panzer unit killed and was severely crippled by a barrage of Thunder Spears from Jean's squad. Jean attempted to finish her off, but was thwarted by the steam emitted from her Titan. Magath rallied the Marleyan soldiers to protect Pieck and bought time for Falco and Gabi to carry her to safety away from her Titan.
Galliard continued to fight both Eren and Mikasa, and over the course of the struggle, raked the crystal surrounding the younger sister of Willy hard enough to create gouges in it. When Mikasa cut the Jaw Titan's leg muscles, Eren grabbed the disabled Titan and used its jaws to crush the crystal above his head. The fluids created by the death of the younger sister of Willy flowed into the mouth of Eren's Titan. Before he could finish the Jaw Titan though, Reiner attacked him with a partially formed Armored Titan. Reiner managed to pull Galliard away from Eren, and Eren decided that they had done enough. He retreated with Mikasa.
The Survey Corps' airship entered the airspace above Liberio and followed the trail of lights previously set up by its soldiers. As the airship came overhead, Eren and Mikasa grappled aboard, followed by most of the other squads. The soldiers prematurely celebrate their victory, having only taken six casualties.
Below them, Gabi chased after the airship with a rifle on foot. She managed to shoot Lobov while his vertical maneuvering equipment was connected to the airship, and by reeling it in, she brought both herself and Falco aboard. Gabi quickly took aim at the crowd of soldiers and shot Sasha Blouse, marking the Survey Corps' final casualty in this operation.
Pieck remembered where she had seen the soldier who had trapped her and Porco Galliard prior to the start of the battle. She identified her to Magath as Yelena, a follower of Zeke Yeager, and a part of the first survey fleet sent to Paradis Island after the Warrior Unit pulled out.
Gabi Braun and Falco Grice were taken prisoner following the shooting of Sasha Blouse and brought to a small room just behind the pilot's cabin. There they found Zeke alive and regenerating his lost limbs. Zeke informed Hange Zoë that everything mostly went according to plan, save for the miscalculations that were the arrival of the Warrior candidates.
Once the Survey Corps returned to Paradis Island, all those previously affiliated with Marley were dealt with. Gabi and Falco were placed in a cell and Zeke was taken to a Titan Forest, where there were plenty of trees for vertical maneuvering and no rocks for him to throw. His Anti-Marleyan Volunteers were arrested by Dot Pixis, who apologized for not being able to trust them.
Though the Survey Corps succeeded in the destruction of the primary Marleyan naval fleets and ports, as well as wiping out the military leadership, by forcing this battle and its accompanying deaths, Eren Yeager broke the Survey Corps' trust in him. The damage to Paradis Island's reputation with the rest of the world was only partially mitigated by the acquisition of Zeke, giving Paradis a Titan of royal blood to go along with their possession of the Founding Titan.
The day after the battle, the Marleyan military excavated the site of victims, which included children. At the site of Zeke's "death," they could only find his limbs, suggesting that he had faked his demise. Furthermore, they discovered that the anti-personnel vertical maneuvering equipment the Survey Corps were carrying contains Marleyan technology. This evidence confirmed Pieck's theory that Zeke was working with Paradis Island and staged the attack on Liberio so he could escape.