The whole unit setup for the Age of Empires franchise has for the most part been for gameplay only, and has seemingly little correlation (apart from uniforms)to the reality of warfare in the times represented.
Skirmishers were regular infantry used to harrass or begin engagements, and were, according to my research, no different with regards to armament than any other regular soldier.
Some snipers/sharpshooters as early as the 18th century were armed with one of the most significant advances in firearm technology ever developed - rifles. Rifling involved cutting a spiral groove on the inside of a gun barrel. This created a tight spin on the round, greatly increasing the effective range and accuracy of a musket.
Up until the mid 19th century, most muskets were smooth bore, and as the name applies were simply smooth metal. They were fairly inaccurate and the thought behind their use was that if you mass infantry tightly together, all firing muskets, then they concentrate their firepower and are bound to hit something. Of course, the downside is that anyone firing on them is likely to inflict a great deal of casualties as well.
Napoleon's tactics included firing a single volley and then advancing with bayonets. It has been estimated that in the typical battle of the Napoleonic wars, about 1 in 30 rounds fired found their targets. So hypothetically, 10,000 soldiers firing 3 rounds per minute and applying Napoleon's 1 volley theory should inflict about 1,000 casualties per minute. With the advent and more extensive use of rifles and conical bullets (most rounds were spherical in shape prior to the mid 19th century) coupled with outdated tactics equalled unprecedented casualties in the Civil War of the United States.
Cavalry had played a significant and often decisive role in warfare for several thousand years. Their domination of the battlefield had steadily waned since the high middle ages, although Frederick the Great, Napolean, and other generals had much success with them, even against modern soldiers. Ironically, these generals modified cavalry tactics, which had involved the use of firearms in the 17th century, returning them to predominantly melee weapon based shock specialists that would disrupt enemy formations.
The thing about cavalry that always baffled me in AOE is their vastly increased health over infantry. Cavalry are simply mounted soldiers, no more difficult to take down than a foot soldier. The thing that really made them a powerful attack force was their mobility and shock effect when charging into enemy ranks, whether with lance or sword. No human being alive can generate the force behind a weapon that a 1/2 ton animal travelling at a charge can add. Cavalry's mobility could allow them attack enemy infantry from the rear or flanks, possibly surrounding a force. This manouver was only devastatingly effective in conjunction with a simultaneous infantry attack. Do a search on the Battle of Cannae to see the effect of surrounding/entrapping an enemy force.
At any rate, AOE is just a game. To try and simulate the elements of real combat would be much too complicated and probably not much fun. Many games have tried, such as table top wargames, but even they cannot possibly account for all the numerous battlefield challenges faced by opposing armies and generals.
[This message has been edited by Hally (edited 06-30-2006 @ 11:31 AM).]