I love horse training! It's such a challenge to teach them to perform certain behaviors when asked!
oh nice, does this mean domestication of horses?
I suppose so! Historically horses have been trained for farm work, sport, transport and warfare!
When did horse train start  in history?
I'm really not sure, but possibly the middle ages. Today, most horses are trained for a variety of recreational and sporting pursuits!
What is the best use of trained horses these days?
Well, I train horses for police and crowd control activities! Some trainers specialize in training horses for movie stunt work or circus entertainment!
is there any government policy concerning how they should be trained?
There is a lot of controversy over the different methods of horse training, some of which could be considered cruel. 
thanks for opening my mind about horse training