Wait. The ryus weren't founded until the peace of the Edo period. How would a person learn in battle and break off from a ryu then?
The ryuha system was around for centuries prior to the Edo period. It was not very popular until the Edo period, but there were quite a few like the Katori Shinto ryu, The Takeuchi ryu and others less known in the west that were around for a good long time before the Edo period.