Yes, that's what I'm saying. I can even give you more details; in order for a horse to be reared, the following must be true:
- the attacker must be unmounted
- the attack must be a thrust
- the attacker's weapon must be of type polearm
- the receiving horse must have a forward speed of at least 4 m/s
- the attacker must be in the front of the horse (120º cone starting from the horse's "center")
- the priority of the animation being currently played by the horse must be less than 74 (riding has a priority of 0, jumping has a priority of 2, etc...)
If all of the above are true, the horse will rear.
Thank you for clearer information cmpx. The only parts I don't fully understand are the meter/second (just not sure how to measure it), and how (or if) an animation played by a horse could ever be more than 74 priority. What comes after the etc?
In battle I've had the chance to attempt a rear on horses of varying speed, and in the video I'll post here I feel like the speed of movement of the horse is nearly identical for the War Spear's successful rear as it was for the Spear attempts. Anyhow it's not especially scientific, and is the best of the first batch of tests I recorded. It's been slightly cut of excess superfluous scenes, and contains 4 separate attempts, the first two with Spear, the third with War Spear, and the fourth with Shortened Spear. I tried to make it clear by setting the items down and hovering over them, though the quality is kind of poor, sorry for that.
Thanks to Septim for helping in those with a STF rider.
We ran some further attempts later but those videos suffered from such horrible recording issues as to be useless, no discerning horse speed at all; just from the experience Winterly and I had, and what others in the duel server were acknowledging, we were unable to rear a Rouncey with Spear, Shortened Spear, and Military Fork. We were successful with War Spear, and also a random Fauchard laying around, as expected. The ponies we tested on were all riding at a moderate speed, fast enough to knock me over in most cases, though in the video you'll see a very slow moving horse get reared successfully by the War Spear, and that was by far our slowest attempt. In the majority of them we just had the rider be a passive third party, not attacking or blocking (though he does block in the second segment of the video above). It could be that we messed up, but it seems unlikely that we would do so dozens of times in a controlled setting. If all polearms are supposed to be able to rear ponies, and weren't intentionally changed, then I guess this could qualify as a bug?