[quote=@Dinh AaronMk]
"Oh this sounds rather amusi-"

>SCP

Nope.

Can this be done without any of that SCP stuff? It lost it's funny a good while ago.
[/quote]
Well, "SCP-186" isn't so much an organism as a location where some pretty nasty fighting went down in real life, and the only real lore I borrowed was transcript SCP-186-56 as follows:

[hider=A Letter From Hell]
Dearest Nadya,

I have heard rumors of the madness happening at home. Be comforted that it is nothing like the madness that is happening here. We thought that four years of war had taught us everything we had to know and then more. We learned nothing.

The damnable Frenchman that the men elected to lead them spoke of peace. He spoke of weapons so terrible that we could make the enemy surrender on the spot. We were fools. We had run at trenches with dead men's rifles and sticks in our hands. We believed him the way we believed anyone that has supplies.

We never thought where this man came from. We didn't wonder why he had the weapons he did. We didn't care. We wanted to live.

We never considered that the enemy had the same things we did. I do not think the Frenchman did either. Or at least I hope he did not. I cannot imagine any man who would walk into this knowing what would happen. Maybe the Frenchman is not a man. Maybe he is something else.
...
I should have run away so many times. The Frenchman gave us a new gas weapon. We refused at first, remembering what had happened in Romania. But he promised us that this was different, that this would put our enemies down without harming them. Who wants any more bloodshed, he asked us. We could not argue with that. We fired mortars at a position ahead of us. A strange blue gas seeped from behind the trees, but the Frenchman cautioned us against advancing. One more thing, he said. He took one of our rifles, and taking aim took a single shot. Before we could ask what a scientist could know of shooting, we heard a scream. He had hit one of the Germans.

He handed me a pair of field glasses. Take a look, he said. I saw the German missing half of his head, still screaming. I have seen everything in this war, but I have never faces like those of that German's fellows as they watched their comrade. The Frenchman, in his terrible calm voice, explained that his shot had to have destroyed at least a quarter of the soldier's brain tissue. Enough to cause instant death, he said. But watch.

I kept watching through the field glasses. The German didn't stop screaming. At least ten minutes I watched, unable to move away. The Frenchman smiled. He smiled at this scene. The gas, he said, ensured that death would not come, regardless of injury. The Germans were too horrifed by their comrade to notice that they were not behind cover, and the Frenchman lined up another shot. The rest of the soldier's head was now gone, and the screaming was replaced by some sort of low grunting, the likes of which I have never heard from men.

No, the Frenchman said, no harm at all. I have bestowed the gift of life on your opponents. Who could possibly stand against that, he asked.
...
We are no longer armies. Not any more. We are animals, trapped in a forest together, uncomprehending. Sometimes, when Volikov sleeps, I hear the Frenchman in the woods, yelling in Hungarian, yelling and laughing. I would almost rather listen to Volikov.

I am going to die in this hole. I am too scared of what is outside of it to do otherwise. Minkin is going to try to brave the horrors in the woods to escape. I am sending this letter with him in the hopes that he does. As I gave it to him, he joked that he will get a civil service commission after the war for delivering a letter from Hell. I am not certain he is wrong.

Goodbye,

Pyotr
[/hider]

Bold emphasis mine.

In theory, I could trace where someone found a pop-sci reference to such a gas (Russian sleep experiment?), and use that instead, but this was more readily-available.
-The rest I'm pretty sure I can throw out.

But in summary, both sides are making zombie-armies of their own definitions and things have started to get a bit out of hand, prompting an international intervention (which did happen IRL, but for different reasons).
-[url=https://www.youtube.com/watch?v=90TW-p3rkQk]It's not all bad, though[/url]