Have you trained a horse be for?
I have never trained a horse before. I have ridden on one when I was younger but that's about it. 
Do you know the ancient soldiers or warriors who fought as calvary where great horsemen 
I have read that. I also think they had to be great horsemen as to ride and carry all of their gear.
Do you know how the African military system evolved over the years?
I am not so much of a history buff. I do not know how they evolved.
They were under a colonial rule,trained by their master's
That seems very interesting. I bet they learned a lot from them.
Nigeria is a west African state named after the prominent Niger river.