"Yes. Well. Whether or not the Neuroi qualify as demons, strictly speaking, I don't know. But they are incredibly dangerous. They burn whole regions to the ground, left unchecked. They don't speak or even think in ways we recognize, though there is clearly some kind of intelligence at work, they fight well enough. And they emerge from a giant eternal storm hovering over what used to be the nation of Ostmark. Neuroi are made of black flat panels that somehow move without sinew or muscle or gear or piston. They can be hurt easily enough. Bludgeons, arrows, mana-blasts, fire. But they quickly regenerate unless one destroys the crystal within, the core. Witches are the most promising combatants - and the only combatants possible against the ones that fly.
As for the UDF itself, we are an international military organization. Our mandate is to coordinate and collect forces from all around the world to more effectively oppose the Neuroi. By taking the ultimate decision power out of any one nation's hands, we can be trusted to defend all nations equally, and not reserve as much for internal defense or petty squabbles over territory, which, sadly, is still happening even with a world-class threat in the field. We're still getting our feet under ourselves in some ways, but we have come a long way in a short time in many ways, thanks to the hard work and dedication of tens of thousands of witches and hundreds of thousands of non-magical soldiers and other staff."