Nearly 300 years ago, as the records say, people were stalked and killed by towering creatures, destroyed outright. Though it lived in fear, humanity found sanctuary in a great fortress constructed by hands whose names were lost to time. Then, one day, the great beasts disappeared, and the people slowly stepped out of their fortress. Leaving it be, they expanded across the lands, erecting large walls in case they came back one day. As time went on, peace mostly reigned, but many seemed loathe to expand further, because of the fear that the monsters would one day return. Any attempt to expand often met great resistance within and without, and thus, man grew content with his place in this world, living in fear of the outside, but feeling secure inside the walls and the great fortress.

The massive outer gate opened, admitting the procession of Survey Corps soldiers on horseback and cart into the village of Zhiganshina. However, instead of heroes returning triumphant, it slowly became apparent that they had suffered many casualties. A boy standing on a box at the back of a crowd marveled at the passing Erwin Smith, leader of the expedition, but right after the commander saw him, making brief eye contact with the boy, a woman burst from the crowd, running towards the troops, begging them to see her son, asking if he returned safely.

One soldier sorrowfully handed her a bundle. In quiet despair, the mother opened up the bundle, revealing a severed human arm, the only remains they recovered of the fallen soldier. The crowd became belligerent, hurling insults and demanding to know if it was the work of Titans, only to be met with utter silence from the soldiers. Over near where the boy, Eren, and his friend, Mikasa, were, two people began grumbling about the Survey Corps, calling them a waste of taxes. In response, Eren began to get belligerent, throwing a stone at the two, but quickly found himself dragged away by Mikasa and hurled against the wall of a random house, scattering the lumber he picked up earlier.

"Hey, Mikasa, what was that about?! I worked hard to pick all that up!" shouted Eren at his adoptive sister. Mikasa berated Eren on his rashness and his determination to join the Survey Corps. Eren, however, mostly didn't care what she thought of it, and simply asked her not to bring it up at home later on. However, it indeed seemed to him that Mikasa was likely to mention this all to his mother when they returned. Grumbling, he picked up part of his scattered sticks, asked Mikasa for help, and the two set off for home once more.

After an argument with his mother over his choice to join the Survey Corps, Eren ran off, Mikasa chasing after him. The two ran into Armin, who was currently being bullied by two older kids. After Eren and Mikasa drove off the tormentors, they helped Armin up and walked through town with him, holding a conversation about some strange rumors of late: lights in the sky, odd trails in the clouds, the silence of the Survey Corps, and the military activity in the capital. Troops were coming in from the districts of the inner walls and the great fortress that stood at the center of the capital was said to have readied its cannons for what could have been the first time in decades. While the conversation circled around to Eren's desire to join the Survey Corps, along with his desire to see the world outside the walls, gossip from the streets often reached the trio's ears.

"Hey, guys..." Armin blurted in a hushed tone, "I've heard that, many years ago, humanity fought a great war with itself, and that Titans also fought one another." This attempt to change the conversation led to a somewhat incredulous response from Eren. "Titans fighting each other? Wouldn't they be too busy killing us to kill each other?" "Well, it's just a rumor, but maybe all of this...maybe it's because they're back, after they've been at war with one another...maybe they've even joined up again..." Eren had no reply to this, instead choosing to direct his eyes at the capital fortress, an imposing structure that stood atop the highest elevation in the land. Protruding from it were many unusual cannons and tall spires. Humanity once made a stand in this very place, it was said, though Eren wondered why much wasn't said of what exactly happened, what came before, or who or what built the fortress in the first place.

At that moment, any train of thought was broken as all three children, along with other passers-by in the main street, began to take notice of a rhythmic, thundering noise. It sounded like great sledgehammers slamming upon earth, and a near-imperceptible keening underlined the odd noise. As the kids ran into the street, citizens stopped dead in their tracks, having never heard such a noise before. As the sound got louder, a slight vibration traveled through the ground everyone stood on. As it steadily reached a crescendo, the tempo of the thumping quickly dropped off, and the noise stopped altogether.

At the time, the vanguard stationed at the top of the Wall ran over and looked down, trying to get a good look at the sudden disturbance. What they saw there, as it stood right outside the main gate, shocked them. It was somewhere close to 20 meters tall, not quite half as tall as the 50-meter-high barrier, but still a sight to behold. Its main body had a blue color to it, while gray limbs were adorned with blue stripes. Its head was shaped like a grimacing, toothy totem, crowning a form that was vaguely bear-like. "It's...a...a...Titan!" one soldier blurted out in shock, a man who had never actually seen one before, but hastily reasoned that that was what he saw. "What are we standing around for? Attack!" shouted their squad commander. At once, the vanguard ran to their cannons, quickly readying them and firing, peppering the giant with grapeshot. The beast noticed this and began to back up, moving its body in a somewhat stiff manner in order to look up, as if regarding its attackers. The men gained some confidence at the sight of the Titan backing up, feeling that they could defeat it. As they were almost ready to fire again, the beast raised its claws.

Back on the street, Eren, Mikasa, and Armin were among the many citizens standing about, gawking at what they could hear and see. They heard the sounds of the wall-top guns going off, and more of the thundering sounds. In the next moment, shock went through everyone as a great flash of green light burst from the top of the wall. Those closer to the explosion could have seen the top part of the wall be vaporized in that instant. The three children were stunned. "What...was that?" asked a trembling Eren. "It...it can't be..." muttered Armin. Just then, a blue light, much less intense than the first flash, was seen from outside the wall, and a scorching sound, not unlike when the troops were blasted away, could be heard. Then, the sound of a cannon, and the sound of an explosion following it immediately, and then the scorching light once more. The great gate that divided Zhiganshina from the outside world began to fracture visibly. As this was happening, more thundering sounds, similar to the original though less intense, could almost be heard through the din of destruction.

For a brief few seconds, the light and sound ceased, giving way to the ominous drumroll outside. When the silence also ceased, the cannon from before was heard again, blasting through the gate, sending burning shrapnel about into the people scattered near the blasted entrance. The blue-and-gray beast revealed itself, stepping through the hole it had made in the once-impregnable Wall. The children were horrified at the sight, shocked and stunned at what had just transpired. "No...it's...a Titan!" Eren choked out. As the bear-like giant approached, two more of the blue-and-gray invaders came forth, both much smaller than the first, but much faster. One was vaguely humanoid, albeit adorned with odd, rectangular protrusions, and held its "arms" above its head, as if bound by invisible stocks. It sprinted at incredible speed, stepping on townspeople who couldn't dodge out of the way and running past the three kids. The other was larger than the former, and slower as well, but still ran at frightening speeds, taking off down a different route. This one had legs more like a bird's, and possessed a squat shape, with an odd "face."

As the Titans strode in, multiple people looked up to the skies to see large shapes descending upon the town, apparently having fallen from some large spheres high above. Some were cocooned in outer shells that fell away as they descended. One of the falling gargantuans and its discarded shell landed at an area Eren recognized-his home. Taking off, with Mikasa following behind, he left Armin alone, in the middle of the chaos caused by the giants' passing.

Armin could barely do anything else other than stand around, paralyzed by shock and horror as he witnessed something he'd hoped would never happen: the return of the Titans.

When he got back to his home, Eren's heart sank greatly at the sight before him. Some large fragment of something-perhaps something that was shed by the falling Titan-had landed on his home. When he found his mother, he was aghast at the sight of her, pinned under a support beam and some rubble. Mikasa, having caught up, joined in to try and free Eren's mother from the wreckage. Despite all their strain, however, they couldn't lift it. The Titan that landed nearby then rose into full view, towering over all of them.

Eren's mother pleaded for Eren to take Mikasa and run, but Eren kept on trying, even when Mikasa began to give up. Just then, however, Hannes showed up, vowing to defeat the Titan before them. As he ran towards it, however, he stopped. The sheer size of the thing, and its stoic, uncaring "face," froze him in his tracks, paralyzing him with fear. Almost as soon as he had drawn the swords from his 3-Dimensional Movement Gear, he sheathed them, running back towards the wreckage, picking up the two children and running off. As Eren thrashed and begged Hannes to let him go, he looked back towards his mother, and the Titan stepping closer. He saw the massive thing raise its foot, and lower it down-right on top of his mother.

As Eren screamed for his mother, trying to shut his eyes, Hannes hoped that they would make it to safety-or, at least, that he could bring the two to safety.

Star Commander Geren Hall was far from pleased at this turn of events. The original idea was to drop outside of the massive civilization while also dropping into the segments of the walled breaching the otherwise impassable wall was necessary, the overzealousness displayed by his Starmates in the Fire Moth and Viper showed a lack of patience. That, combined with the drops over the town itself, would not look good once the whole Trinary made their report on how the initial insertion went. Perhaps it couldn't be helped, though-this world was so deep in the Periphery that it seemed to be cut off from the rest of colonized space. Not only that, it seemed to possess a Castle Brian, and attempting to drop on top of that was unlikely to succeed. Great Father above, how did these Freeborn manage to subdue that? Seeing the carnage that Bliner and Quin caused made the Kodiak pilot shake his head. This whole Trinary had probably just soiled its chances to get the civilians to cooperate.

However, as the ancient Terran saying went, the show must go on. For Clan Ghost Bear, this invasion force would have to make a show of power to hopefully convince the native defenders to back down. As Hall began broadcasting a warning to any enemy forces over all open frequencies, he kept noticing the many people running from his BattleMech-all of them looked like they had stepped out of historical archives of ancient Terran civilizations, dressed in somewhat medieval garb and running in a panic out of antique-looking buildings. Clearly, civilization had deteriorated on this world. The question was, did these people know what BattleMechs were, or were they running because they never saw one before? How much had society declined on this backwater world?

Clearly, claiming the world in the name of the Clan was not going to be as simple as previously thought. We should not have gambled so low, we may need more than one Trinary for this...

On that day, humanity received a grim reminder of the fear they had of the Titans, and the humiliation of being trapped like a bird in a cage. For the Warriors of the Clans, however, they were shown a stark example of a world left to its own devices.

A/N: You might have seen this coming because of how it's categorized on the site. This was an idea I had back when the anime was airing, and I don't think anyone else thought of this, so here we are. This will remain a one-shot, though, I'm not up for re-doing all of AOT with mecha. As for how it could fit in the canon of BattleTech: again, it's a Deep Periphery planet that once housed the Star League before being cut-off.

Attack on Titan is created by and belongs to Hajime Isayama. BattleTech is currently created by and belongs to Catalyst Game Labs and Topps.