It was the arrow slits that did us in.
We made 'em so our archers could fire out, under the protection of our stonemasons. We made 'em to keep our people safe from the outside. But the blinkers...they go wherever they want, wherever they can see. Just two of 'em made it into our bailey, and the archers never knew what hit 'em.
The rest of us had some warning, but we could never tell what direction they came from. Second story windows in a lot of our buildings meant the emotionless bastards could enter through the door on one side, and come down through the bedrooms behind. There was no wall, no defense against them, they were like rain, like air, finding every crack and flowing in and running us through.
They knew our layout, too. Of course they did. A thief of theirs found the plans for the town in the belongings of the chief engineer, robbing his house. They waited 'till he was gone, and simply blunk into his house, ransacked the place, and, five minutes later, blunk out. There was no sign of forced entry, of course, so when he came back, he came back to one of those things in his house. Guy never had a chance to draw his blade.
The worst part about this is that we knew what they could do. We had seen it, just hadn't really thought of it. When our people caught that thief, they ripped out her eyes -- can't blink to where you can't see, right? We thought that would stop them, serve as a warning. I don't know that it didn't serve as a provocation. Looks like they don't take kindly to them that thwart the blink.
When the war was joined in earnest, the pikemen were useless. Don't really matter how big your spear is if your target can just *poof* behind its point. Shields, too, not the best - little twinkly sparkle-jerks can get behind you with a nod of their head and a woosh of leaves and grass.
Listen, you can't STOP these guys. Not 'less you rip out their eyes. That's why I wear this necklace here -- eyeballs of the bastards, harvested from those I kill. I hear they're the reason goblins live in warrens, too: those poor blighters have been their victims from time immemorial, and twisty tunnels limit the damage they can do. Still, I don't know that the goblins weren't once folks like us -- fighting these critters turns you INTO goblins, making you hide in warrens, seek the security of darkness....we'll all be goblins sooner or later.