Most of Wall Maria was still standing after its fall. Its enormous stone barrier had not been smashed into rubble from end to end. Yet humanity had to abandon the vast territory behind it.
How can a fortress be almost completely intact and still be a total failure?
Because the Titans did not need to destroy every stretch of wall. They needed an opening—and humans could scarcely remove the intruders once they got through.
Two gates, one massive disaster
In the year 845, the Colossal Titan kicked through the outer gate of Shiganshina District. The Armored Titan then broke the inner gate, opening a passage into the land protected by Wall Maria.
Calling the breach a “tiny hole” is a joke about perspective. Those gates were enormous, but the damaged sections were tiny compared with the full length of the Walls.
A wall is only an effective barrier while the route around it remains closed. Once invaders can pass through a gate, all that impressive masonry elsewhere is doing very little to stop them.
Imagine installing the world's toughest vault and leaving the door open. Now imagine the burglar is a Titan.
Regeneration makes every intruder unusually expensive to defeat
Titans heal damage that would incapacitate ordinary soldiers. Severed limbs can regenerate. Defeating a typical Titan requires attacking the vulnerable area at the nape.
That makes ordinary firepower far less decisive. A missed strike buys time, but does not necessarily remove the threat. Soldiers using maneuver gear have to approach a huge and dangerous target to reach the weak spot.
The imbalance gets worse: Titans do not need food shipments and conventional resupply the way a human army does. Human soldiers require equipment, horses, rest, medical care, and food.
The attackers recover while the defenders spend irreplaceable lives and resources.
The land survives, but the way of life does not
This is the cruelest part of the setting. A Titan does not need to hold a town hall or burn every farm to make a region unusable.
People need to cross roads, work in fields, bring supplies into towns, and let their families move safely. Titans roaming around can disrupt all those activities.
The buildings and fields may remain. What disappears is the ability to live there safely.
That is why a seemingly localized breach can have consequences across an enormous region.
Why not simply kill them all?
Because every Titan requires a dangerous fight, and the intruders are scattered across a huge area. Finding them, reaching the nape, and surviving the encounter already demand enormous effort.
Worse, if the gates remain open, more Titans can enter while the soldiers are trying to clear the existing ones. It becomes an endless and costly cleanup job.
The logical first step is to close the entrance, then work on securing the territory behind it.
Why sealing the gate was a strategic breakthrough
Eren's hardening ability made it possible to attempt exactly that during the Return to Shiganshina operation.
Sealing the opening would not instantly eliminate Titans already inside Wall Maria. It would, however, change the problem from an uncontrolled invasion into a territory that could eventually be cleared.
That is the dark joke at the center of Wall Maria's fall. Humanity built an almost unimaginably large fortification, only for a pair of broken gates to make much of it useless.
The entire continent-sized security plan turned into a question of whether someone could shut the door.
And unfortunately, the repair crew still had to fight the monsters on the other side.
