The horsethief.

"Quickly!" Whispered the thief in the darkness, his body covered in soot and horse-sweat. Unpleasant as the combination was, he was used to it. Strange man-smell would drive the horses into panic, but strange horse-smell they wouldn't care so much about. We need to be holding the reins of enough horses and leading them away before the next stage in the plan, he thought to himself. The others crept in, too noisy for the thief's liking. "Fools," he muttered to himself. You work with what you are given, his brother always used to say. Then he had gotten himself killed, rebelling against his liege-lord by allying himself with poor, disgruntled farmers. Fat lot of good that piece of advice had done to him.

The fellows he had with him were not bad though, and soon enough they had reined in some two dozen of the finest horses, and led them away.

When the others were a safe distance away, the thief singled out a tame mare. "I'm sorry, my friend," he said softly, as he unsheathed his knife and opened the beast's throat. The smell of blood drove the remaining dozen score or so animals into a frenzy. An alarm was taken up, and men started rushing out of their tents, some immediately trampled by the manic horses.

The thief knew that they were fighting an unworthy foe, for no knowledgeable battle commander would house this many untrained horses together.

A lone horn blew a long and quivering note, a few hundred paces south of tents. Seconds later the men in the tents could hear the thunder of hundreds of hooves coming closer. Before anyone could find their arms the enemy came upon them, bearing lances and axes and torches. The cavalry hacked, burned, and drove through everything. Only the three big and colourful tents in the middle were allowed to remain standing, the rest was razed mercilessly to the ground, and the soldiers with it. The battle was over before it had begun, their own horses had seen to that.

The thief had slipped quietly into the surrounding night.
*****

PS. Somewhat of a standalone. I've kinda given up on my fan fics and have been wanting to write something set in some kind of a medieval setting. With destriers and heavily-armoured knights and archers in the darkness. Maybe it has something to do with all the George RR Martin I just read, or maybe it is all the Age of Empires I've been playing that is talking. Even so.