It had been a normal day, nothing out of the ordinary. Not a peep from the outside world, the guards stationed at the entrance to the caves changing shifts as routinely as ever.
The boom that sounded a few minutes later shook everything in the northern section of the cave system, sending debris clouds into the air and toppling over smaller projects and possessions. For those deeper in the caves, the suddenly red lights sent notice, spurring the soldiers and healers alike into action. Two squadrons readied themselves just outside of the barrier to apparate aboveground in the hopes of not drawing attention to the exact location of the cave, while another two hid in the elbow of the entrance corridor, ready to defend.
In the open air, they were met with a small army, some of them wearing strange equipment on their shoulders. Throughout the battle, these were the ones most likely to drive themselves into even the most unsurvivable situations, and most of them died fairly quickly. There were other explosives with them, and a few more went off, causing minor ceiling collapses below as the cave defenders battled above. The two squadrons weren't quite enough to distract them from the entrance, a small faction breaking off to go searching for just that, and finding it. Fortunately, thanks to those defending in the tunnel, none survived to tell the others.
Despite the surprise battle, their attackers didn't quite have a big enough force after the death of so many, calling a retreat after a little over an hour. Two were captured, but the rest died or fled the scene, leaving those still standing on the side of good victorious.