One of the most significant events in Attack on Titan is the Rumbling. The Rumbling is a fail-safe King Karl Fritz created to keep the Marleyans attacking Paradis Island. Hundreds of years later, Eren uses the rumbling to save the people of Paradis Island from enemies outside their island. What is the entire history behind the Rumbling? How does this fail-safe give Paradis Island a fighting chance against their enemies, and how will it destroy the world?
The invention of the Rumbling starts with Karl Fritz and his mission to create peace for as many Eldians as he could. Karl Fritz dreamed of a world with no war, taking them to Paradis Island. To ensure this, he used the Founding Titan ability to wipe the memories of everyone on the island and create the three walls. These walls weren't ordinary, though. They were filled with Colossal Titans, waiting to destroy anyone who dared attack them.
Warning: Major Manga Spoilers Below
Karl Fritz and the Rumbling
With the help of the Tybur family, Karl Fritz ended the reign of the Eldians. King Fritz hated the bloodshed and power-hungry history that his ancestors had. He believed the best way to end it was by allowing the Marleyans to take over and escaping to Paradis Island with as many Eldians as he could take. King Frits wanted only peace on the island, but he knew that the Marleyans wouldn't allow this. Not after years of enslavement and bloodshed.
So, King Fritz created an ultimatum. King Fritz made Collosual Titans that he trapped within the three walls Maria, Rose, and Sina using thousands of his people. Sending a message to Marley, King Fritz threatened to unleash all the Colossal Titans on the world, starting the rumbling killing everyone outside the island. This prevented Marley from attacking the island, except King Fritz never intended to start the Rumbling. Instead, if Marley or another enemy came to attack, he'd allow them, believing that they all deserved this fate.
With King Fritz erasing the people's memories within the walls, the Rumbling was forgotten by most. For years the people inside the walls believed that the walls were made from stone until Eren and Annie's fight. Revealing the truth hidden by the Church of the Walls and the royal family.
Eren and the Rumbling
Being the new and final holder of the Founding Titan, Eren is the only one to activate the Rumbling. With Marley coming in to attack Paradis, many want Eren to start some of the Rumbling. By only commanding the titans within Wall Maria to destroy Marley. Allowing Paradis about 50 years to catch up on knowledge, medicine, and technology.
Armin and the others know that the only trump card they have is the Founding Titan and the Rumbling in the world outside of the walls. Without them, they would be powerless against the forces beyond the island. This is the only weapon that gives Paradis any power, but Eren has different ideas. Instead, Eren wants to destroy the world by activating the rumbling to its fullest. This would mean thousands of Colossal Titans would be released, flattening the Earth and killing everyone off of the island.
Eren's goal isn't to gain time to catch up but to stop all attacks from ever happening. Eren wants any potential threat destroyed before they can attempt an attack. This goal shapes the end of Attack on Titan, with Mikasa and the other's tasks to stop Eren from destroying the world. Thankfully they stopped Eren and ended the reign of Titans for good, but the manga's ending sheds some light on Karl Fritz, the Rumbling, and its true purpose.
The Rumbling was never meant to end the world or stop enemies from attacking. In the end, the Rumbling accomplished Karl Fritz's goal of ending the war. At least ending the conflict between the Eldians and the Marleyans. King Fritz never intended to start the Rumbling, but as the holder of the Founding Titan, maybe he knew Ymir's wishes of ending all titans. This would mean Fritz created the Colossal Titans for Eren to finish everything. This would explain why Karl Fritz, a man tormented by his ancestor's past, willingly sacrificed so many of his people to create the walls.
The Rumbling cleansed the world of the past and the Titans. Sadly it also caused the death of Eren Yeager, a young man who wanted to be free. Rather tragic since Eren's entire life was planned out by Ymir and the other Attack Titan holders. I suppose it means that no one is truly free and that things that appear evil can be used for some good. At the end of everything, a bird wraps Mikasa's scarf around. Could this mean Eren is finally free?