My great-grandfahter was a Cossack from "Then Russia" "Now Belarus" where the Belarus, Ukraine and Poland borders met, but I don't now which "type" like Don or Kuban etc. He fled from the place he lived about 1912-1914.
My great-grandfather is the man in the middle and his brother is sitting to his left (both are cossacks).
I think he was a Don Cossack but I can't find someone with the same uniforms.
I know almost nothing more since he never talked about what he did in the military to my grandmother.