Bryce, I can't speak with any authority on cavalry operations, but in the infantry the strongest, steadiest unit was often placed on the right to anchor the line of battle and set the pace forward -- the other units guiding on the right. There was an element of the 4th Infantry Division in Vietnam (I forget just which outfit at the moment) whose motto was "The Right of the Line", harkening back to its roots as a Union regiment in the Civil War. As I recall, a staff officer asked the brigade commander where to position that particular regiment; to which the general replied, "To the right of line, of course." That was considered to be a position of honor. A hundred years later, in Vietnam, the outfit was still proud of that; hence, the outfit's motto. I wish I could remember just which unit it was.