Russia Ultra VH/VH

3 Units of standard melee cavalry early on to take on non-line infantry or pre-plug bayonet line infantry which are already in a shooting match. Will slaughter the unit. The 3 units can all approach from one flank.

3 units of standard melee cavalry can slaughter one unit of light infantry if they approach from opposite sides.

2 units of cavalry charging a unit of any infantry that is in a line and already in melee with its equivalent unit.

1 unit of cavalry for charging down an undefended cannon. I prefer using terrain and engaging them with a infantry unit in hand to hand. Not recommended for the general.

1 unit of cavalry for each of the compass directions to hunt down retreating enemies (highly recommended for the general).

In general the enemy has to be pre-occupied with something else or you need equal numbers and flank attacks. The biggest bonus with cavalry is that they move fast and you can separate up the enemy like lambs from a flock. If the enemy gets divided up enough then cavalry can be very good. They are not shock troops in ETW so they shouldn't be used to break enemy formations by direct attack. By maneuvering around them the enemy will divide its attention between cavalry on a flank or behind and cannons and infantry to the front. Once the enemy has committed its forces it is then best to have as many of your cavalry engage the enemy at its weakest point. My order of preference of units that are separated out from the herd to knock off would be general/artillery/cavalry/light infantry/line infantry.

The other use of cavalry is as bait to funnel the enemy into a prepared position. Particularly useful if you have static cannons.