That's exactly what they would have done.....broken the horse in to saddle/bridle and eventual riding.
If you G**gle 'Horse breaking techniques' you should come across sites explaining how it's done.
It's only recently horse 'gentling' has come into vogue, prior to that it was a rather harsh job....tie the colt up, slap a saddle on it's back a bit between it's teeth and jump on

An interesting article.
http://www.rootschat.com/links/07xc/Barbara