REPLY:  It's tough when you are round penning aggressive horses like this -- and this is aggression! And something that is very important to turn around ASAP. What I do in cases like this is...first...have someone man the round pen gate, so they can open it fast if the trainer inside needs to exit quickly. I take in with me there my 12' lead rope (it's a heavy rope to spin vertically, smacking the ground hard with it as needed and the horses IS going to run into that spinning rope wall if he enters my space unasked for), but I also take with me my training wand with plastic tied to the end, to shake in the air (in the direction of the horse's head/eye) and push off the horse with that. Something about having those TWO visual barriers going on at the same time (one in each hand) can short-circuit a horse's brain and make them think twice about attacking/coming at you aggressively. If that doesn't work, as a last resort, you can use a squirt gun, pointed at the face (as your second object along with the rope to spin). It doesn't hurt the horse, but makes them think twice about the attack, and has them backing off. This horse has big time learned to move the human's feet and that is sooo dangerous, therefore, very important to turn around, starting with the round pen exercise. Do any/all of the above to stop his attacking type behavior and get him focusing on you, the leader, and backing off, for a start. If you feel inside that even that is too dangerous at first....

What you can do for a start, to keep you safer at first...try getting him to move from you positioned OUTSIDE the round pen, via spinning a 12' lead rope and smacking the outside of the round pen if necessary and also you can use plastic tied to the end of a training wand as well there. With a goal there being to just move his feet away from you. Usually if you can set up that "wall" that they are going to run into, they'll not want to close that attacking-space between you and you can begin the round pen exercise with them protesting less.

I want to stop here and direct you to a link on my web site that shows an aggressive clinic horse I trained, so you can see some of this in visuals, as well as more explanations -- want you to see this in action & you'll get more ideas there: http://www.naturalhorsetraining.com/ClinicPics.html

When round penning a horse who has more fight then flight at first, it's real important to take safety precautions, like: wear a helmet when you enter the round pen; have someone in charge of the gate, to open it quickly for you if needed, and maybe even have them hold a wand with plastic tied on the end in case they need to step in and rescue you; don't enter the round pen until you see the horse has calmed down/chilled in there for a while -- if you have to, start your instructions to the horse from the outside at first, showing them that you are in charge of their feet, even from the outside, and definitely "claiming" the gate area for sure. It's not about trying to scare the horse, but about being assertive. And postitioning yourselves as "lead mare" of their herd and showing them: you are in charge of their feet, not them.

Your horse there horse actually sounds like a stallion. Are you sure he's been gelded correctly? If you're not sure, read this link on my web site about that:

Proud Gelded/Proud Cut/Cryptorchid Horse - Behavior when studs are not gelded properly

Another idea, if you feel you're not making progress with the above...I had an NH trainer friend of mine pass to me what he did with a seriously aggressive breeding stallion (worth a fortune!) that had attacked & put a vet in the hospital, and no one could get near him without the horse attacking! The trainer was called in to see if he could turn this horse around, or they were going to have to destroy him (very expensive horse, in the hundred thousands!). Since the trainer couldn't safely get into the round pen with him at first, to start his retraining, without the horse attacking him...he used water balloons to teach the horse to respect his space and to back off from attacking (this is extreme, but nonviolent, and was the last chance this horse had to be turned around, or he would have to be put down, it was that serious a problem horse). As the trainer entered the round pen with his rope, and wand with plastic, and if the horse was clearly not going to back down, he had water balloons in a shoulder bag he was carrying, ready to fire off, and he tossed it in the horse's face when the horse tried to attack. Well...of course, you know how water balloons work! It explodes with water on impact, but disappears instantly, so the horse had no idea "how that happened." It seemed magical to the horse and the trainer suddenly seemed "all powerful" and worthy of listening to suddently. Didn't hurt the horse a bit, but stopped him in his tracks and allowed the time frame for the trainer to direct his feet away and start moving him around the round pen. It took only two water balloons and the horse backed off and started listening for the first time in his life. The trainer could then switch to using just the rope to spin and the horse progressed there beautifully. He retrained into quite a wonderful, well-mannered horse, in the end.

I'm telling you this just to show you the far extremes one might need to take at the very beginning with some really seriously aggressive horses, but it's only at first. Once the horse backs down and begins to listen there, things start going like clockwork, normal learning curve.

Don't let your horse make inside turns at first either as you get them moving around the round pen or that inside turn could easily switch into a charge into you at the beginning (before they've made an attitude switch). You're not going to allow the inside turn there (only outside turns) until you see the horse show all 4 signs of compliance that I go over in my Round Pen Leadership DVD. Once they've settled down, are more compliant and are showing you those 4 signs, then it's safer to start allowing the inside turns. But at first, if the horse tries to do inside turns unasked for, up the pressure and push them back into an outside turn.

If the horse backs into you there, by the way, and seriously tries to kick you, that is: war. Use the spinning rope as a "space barrier around you" that he will run into and it'll smack his rear (a long length of the rope!! Don't get too close in there--let the rope do your talking there) -- he will very well know he did it to himself, all by himself there --  to let him know that backing up aggressively to kick you, and refusal to move off and away, is just not a choice there. Get as assertive as you need to, to show him the black & white zone. Black zone is the behavior he absolutely is not allowed, and that usually involves your own safety. Pressure is applied (as high up the volume instantly as needed) when they step into the black zone. Pressure is lessened, or removed altogether, when he's back in the white zone (acceptable behavior).

Give what I've gone over a try, be safe, think your strategy out ahead of time, and have all your ducks in a row before you begin. And you should be able to work your horse past this issue pretty fast.

If you ever feel this horse is just way "over your head" training-wise, or too dangerous, don't hesitate to call in a natural horsemanship trainer to help you one-to-one there to get him back on track. I have a list of NH trainers that starts here: www.naturalhorsetraining.com/FindNHTrainers.html

Hope this helps!