Shanxi was a mistake. Take it from a Turian who was there.
At first, with the domination of our space forces over the System Alliance's, it seemed that we'd have an easy time of it. Oh don't get me wrong, the Alliance forces put up a fight, but they were ridiculously outnumbered and outmatched by the 3rd Palaven Expeditionary Fleet.
We were so confident when we began orbital landings. Sure, we lost a few transports once we hit atmosphere, but that was to be expected on any orbital landing operation. Problem was, we didn't pay attention to how those transports were taken down.
The initial battles went in our favor, easily sweeping the human forces aside. The first city we came across fell easily, the defenses having been taken out by an EMP from the drive core of a frigate overloading overhead as it fell out of orbit. After that though, it started to go downhill.
It was when we put the capitol under siege that we first saw them. At first, it was just a rumor, you know? Stories of humans committing superhuman feats. My favorite at the time was the story of a human soldier picking up one of their treaded tanks and throwing it at one of our squads. We laughed it off at the time, saying that the gizzard-heads had gotten spooked when an explosion sent the tank flying. Our conception of that didn't last long.
We were trying to take a building, some office or another, but the humans were well entrenched, with all but the front approaches impassable due to rubble from collapsed buildings. So, brass sent in a Cabal unit, you know, one of the Heirarchy's biotic shock squads. They went in the front, and then, the whole front of the building just exploded.
When the dust cleared, the Cabal were gone. Instead, there was a single human standing where the entrance used to be. Oh, we all laughed at the human's audacity, right up until he raised his hand above his head. We stopped laughing alright, especially once the buzzsaw of yellow energy he conjured cut through a swath of good Turians. Literally, the buzzsaw, Destructo Disk it was called, cut them all in half. We tried to shoot him down, but small arms fire just bounced off of him. Before we could bring anything heavier to bear, he flew off. Yes, flew. Without any apparent aid. We didn't have clue how to report it without sounding insane.
As the siege continued more and more reports of these flying humans, what our prisoners called ki-users , came in, each one detailing how one of these humans had taken out an entire squad or flipped a tank or three. It got to the point that we were calling in entire artillery batteries to bear on these humans whenever we saw them. Not even they could withstand high explosives. Eventually, we managed to take out most of their Ki-users, and started to gain ground quickly. We were on the doorstep of their central command.
We thought we had won. We were wrong.
The fleet didn't realize that the five small contacts on radar were anything but meteors until they hit the atmosphere and started to slow down. The ground pounders didn't know anything was wrong until the ships, no more than small one-man pods with propulsion and life support, crashed into the ground, leaving five craters in the middle of our main forces.
Five humans came out of the ships, a stylized Z emblazoned on the breastplates of their obviously personalized hardsuits. Those five humans singlehandedly destroyed any hope of taking the planet. Whole battalions were wiped out with a single gesture while others were buried alive as the ground underneath them erupted with sourceless explosions. Nothing we did worked, artillery fire not even fazing them. One of my buddies from another platoon swore that he saw one of them catch a missile and break it across his knee.
Not even the fleet was safe from them. When General Oraka tried to have the fleet take them out with an orbital bombardment, two of them flew into orbit and began to take our ships apart with their bare hands. The carnage didn't stop until command surrendered.
It was that day that we learned why no one messes with the Z Corps.