A further note on the use of cavalry:
Some will tell you that cavalry is useless, but nothing could be further from the truth (at least against the AI). The key lesson to learn is just that you should NEVER let them within shooting range of enemy infantry. But give them a nice flank (or a long column) to charge, and they can easily be used to rout two or three units in every battle.
The key is charging at the right time (to get the charge effect), preferably with more than one unit, and to not engage the entire enemy unit at once. One dragoon unit of 75 men WILL get killed by 120 infantry, but if those 75 men are charging a small portion of a thin line, the infantry will rout long before the entire unit becomes engaged in battle. When your cavalry becoming engaged in a massive swirling melee against infantry, you should always consider very strongly whether you should pull them out of the combat.
In addition to their battle usage, cavalry is also very useful as an attention getter. See the AI marching its entire heavy column of infantry toward your army and worried that you won't be able to beat them back? Send some of your dragoons around their flank and watch as the AI detaches several regiments to chase your men. Just make sure to keep your cavalry out of range while the rest of your army kills the remainder of the infantry.
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