Tarheel wrote: I probably should have called this an 'opportunity charge' instead...I think I mixed up my terms.
I'm not suggesting the cavalry is looking to do something outside of its usual role, I'm suggesting that the cavalry is 'harassing' the advancing infantry formations with a hasty opportunity charge.
In my view, this is outside the usual role of cavalry.
The role of cavalry can be divided by type.
Light Cavalry had a primary role of scouting, and driving off enemy scouts (screening). Light Cavalry were therefore only really interested in enemy cavalry, and infantry were beneath them. If engaged by infantry, they drew back. On occasion they were ordered to engage the enemy infantry or guns as a mass charge (e.g Somosierra), but they weren't designed for this role. More typically they were held back for the pursuit of routing infantry.
Heavy Cavalry were shock cavalry, and operated en mass, and in specific charge attacks. They were considered a decisive arm of attack, and cavalry leaders who got engaged in minor skirmishing were not well regarded. Good Heavy cavalry was highly disciplined, conducted well formed charges, and reformed at command. English cavalry was infamous for it's poor discipline in this regard. However, Heavy Cavalry was in decline due to the increasing power of firearms (and incidentally had a similar problem against long bows in the 100 Years War).
In both cases, I just don't see cavalry used for 'harassing' infantry. Heavy cavalry was far too valuable, and Light Cavalry weren't much use. Cavalry was primarily concerned with enemy cavalry, and from time to time capturing gun positions (Raevski Redoubt). Light Cavalry was far more useful scouting, screening, and in pursuit. By the time the US Civil War came round, Light cavalry were the only cavalry (and often used dismounted), and by WW1 cavalry couldn't withstand the firepower.