| This article or section does not cite, or does not have enough references or sources.|
Please help improve this article by introducing appropriate citations.
|If you ever try to interfere in our affairs, the tens of millions of Titans that sleep inside the Walls will surely flatten the entire earth.|
|— Karl Fritz's final words to the outside world, recounted by Grisha Yeager|
The rumbling (地鳴らし Jinarashi?, also translated as earth-shaking) is a hypothetical cataclysmic event involving Karl Fritz's Wall Titans marching across the earth, destroying all life upon it. It was a key deterrence factor for the Subjects of Ymir on Paradis Island until the year 854 when Eren Yeager unhardened the Walls and began the rumbling.
During the final days of the Great Titan War between Marley and the Eldian Empire, King Karl Fritz used the power of the Founding Titan to raise three Walls on Paradis Island: Maria, Rose, and Sheena, each named for the three daughters of Ymir Fritz. These Walls were constructed from the hardened flesh of countless Colossus Titans created with the Founding Titan's power.
Upon gathering the remnants of the Eldian Empire into the Walls and closing the gates to the outside world, Karl Fritz issued one final declaration which assured the enemies of Eldia that if Paradis were to come under attack, the Founding Titan would unleash the Wall Titans to trample the earth into ruin. However, Karl Fritz secretly confided with the Tybur family and the remaining Fritz family on the mainland that this ultimatum was an empty threat of deterrence. In truth, Karl Fritz made a "vow renouncing war" with the Founding Titan ensuring that none of his successors would use the Founding Titan to threaten the world again, allowing for Eldia to live in a brief paradise before their enemies would arrive to destroy Eldia as Karl Fritz believed they deserved to be.
As Karl Fritz had hoped, no open declaration of war or act of aggression was made against the people of the Walls for over a century, though Marley would use the lands beyond the Walls on Paradis Island as a penal colony for criminal or undesirable Subjects of Ymir transformed into Pure Titans. However, over eighty years after the end of the Great Titan War, Marley's declining military industry turned the nation's attention towards Paradis and the fossil fuels hidden beneath Eldian lands. Despite the vow renouncing war being known to Marley through the Tybur family, the threat of the rumbling was too great a risk to attempt a full scale invasion. Instead, Marley began training the Warrior Unit in preparation for the Paradis Island Operation, an infiltration of the Walls with the power of the Titans that would not provoke the attention of the King of the Walls with military force.
In the year 845, the power of the Attack Titan causes Grisha Yeager to inherit future memories from his son Eren, revealing the Fall of Wall Maria later that day. Grisha flees to the chapel of the Reiss family where he is influenced by the will of Eren in the distant future to steal the power of the Founding Titan and slaughter the Reiss family. The future memories of the Attack Titan reveal to Grisha the sight of the rumbling that Eren will create.
During the Survey Corps's attempt to capture Annie Leonhart, a portion of Wall Sheena in Stohess District is damaged by Annie's Female Titan, revealing the face of a Wall Titan within it. This revelation causes great confusion among the Survey Corps and panic in Minister Nick of the Church of the Walls, demanding the Corps to cover the face of the Titan before sunlight could reach it. The presence of the Titan in Wall Sheena leads Squad Leader Hange Zoë to quickly deduce that all of the Walls must contain Titans within them. This creates unease among soldiers such as Armin Arlert, who wonders at the possibility of all Titans within the Walls emerging to walk.
Upon discovering the journals of Grisha Yeager in the Yeager family's basement in Shiganshina District, the Survey Corps learns of the nature of the rumbling as a deterrence factor that has kept enemies of Eldia away from Paradis Island for over a century until five years ago. During a gathering to discuss the findings of Grisha's journals, the leaders of the military in the Walls discuss how the power of the Founding Titan to release the Wall Titans may be achieved despite the vow renouncing war. Recalling his encounter with a Titan whom he later realized was Dina Fritz, Eren Yeager realizes he can still bring out the Founding Titan's power despite his non-royal blood as long as he is in contact with a royal-blooded Titan, though he keeps this realization to himself for the sake of Queen Historia Reiss.
Shortly afterward during a ceremony honoring the survivors of the Battle of Shiganshina District, a moment of contact between Eren and Historia opens a glimpse into Eren's future memories where he sees himself influencing the decision of his father Grisha in stealing the power of the Founding Titan and slaughtering the Reiss family. At this time, Eren sees the sight of the rumbling that he will cause in the future.
One year after the failure of the Paradis Island Operation, the inhabitants of Paradis encounter the Anti-Marleyan Volunteers, a secret organization of Marleyan soldiers conscripted from foreign nations who all wish to aid Eldia against Marley with the help of Zeke Yeager, who inherited royal blood from his mother Dina Fritz. Through the Volunteers, Zeke proposes cooperation with Paradis to bring Zeke into contact with Eren, holder of the Founding Titan's power, to begin a small-scale rumbling which will further deter enemy attacks until Paradis can reach a point of technological advancement sufficient enough to no longer rely on the power of the Titans for protection.