Sorcerous empire in the Attack on Titan world

Convoy

"I said you are all under arrest!" the man with a unicorn on his jacket shouted at the members of the Survey Corps ahead of the small Imperial convoy.

....

Everything had been going fine! The Albert fit rather awkwardly through the gate to the so-called Wall Rose and Wall Sina, but they fit and were necessary for the trip back.

Regardless, the civilian population had reacted... oddly.

Oh, when the horse-riding members of the Survey Corps rode through, they were cheering, ecstatic to have their land back, or at least, having won a victory against a supposedly invincible enemy. But the second the first Humvee drove in, they got quiet. Then the MRAPS followed, then a pair of ATs, and finally four Albert, tank crews awkwardly waving as they drove by, as by that point everyone had at least switched from uncertainty to curiosity.

The streets had been tight, but the convoy made it through without any real problems, and it had been smooth sailing from then until they reached Wall Sina. The members of the Military Police were, for lack of a better word, visibly incompetent. Despite Erwin sending messengers, the MPs hadn't even said anything when the Imperials drove in after the Survey Corps, just staring in silence, some looking downright frightened.

Then they were making their way to the center of the interior wall when they met several of these Military Policemen who stopped the convoy. They introduced themselves by raising their muskets, some of them bringing out small cannons even.

Before Erwin could even ask, the visibly nervous commanding officer for these idiots in uniform declared that they were to be arrested!

It really didn't help that the MPs looked nervous as hell, and none of them were following the basic rule of trigger discipline, the perfect environment for a gun to go off accidentally, something every competent soldier there understood.

"Dude, tell the SS ahead to gun it, I seriously think these guys are gonna shoot first," Dave stated.

"Dave, you will stay quiet!" Mark hissed in an angry, almost parental tone.

They had four tanks, but the MPs did not.

They had fully Magical automatic rifles capable of piercing just about all body armor available in a pre-industrial society, the MPs did not.

They had armor and armored cars, but the MPs did not.

Also, they are physically stronger

But still...

"Forget that, I'm checking if-"

Before he could check the radio, it crackled to life with a very irritated-sounding voice.

"Anyone listening to this; hold your fire, sit the hell down, and don't do anything stupid. Let our commanders do the talking; this is probably just a misunderstanding."

Levi.

The admittedly short officer had moved his horse towards a Humvee and grabbed the radio, probably intending to relax the troops... or at least to order them to relax.

Mark shifted nervously at the way the voice sounded like it was somehow glaring directly at them despite being a message to everyone with a radio.

The Survey Corps captain was already leaving a mark on the Imperials.

"Captain, what is the meaning of this?" Erwin asked the visibly nervous officer.

"Uh... These people are from outside the walls! You declared as much in your let-"

"The entrance they came through is situated within Wall Maria, not beyond it. And if the king did not wish to meet our allies, or have them arrested, then why not send word sooner? We outnumber them after all."