About baggage: the roman army learned to travel without it, all the provisions carried by the soldiers themselves. They each had their own cooking set, bag of wheat which they milled and baked themselves. A group of soldiers had a joined tent so each carried a part of it.
About supply lines: basically you have two options.
One: you carry everything with you and resupply from the rear. The enemy will harass the supply lines, which means you must direct men to guard the rear instead of fighting on the front. This was what killed Hannibal.
Two: you live off the land you conquer. It means you can travel fast but it can always turn against you if the enemy burns their own land to destroy you. Napoleon experienced that when he marched on Moscow, along with every other conqueror of Russia (Germans in WW2).
On the march - Human beings are reasonably sensible. Time and again simple soldiers prove that an army on campaign is an army that can travel light. During Sherman's grand march through Georgia (God save the Union tongue.gif) one of his bummers was kind enough to keep a good diary. In it he explained that he cut his blanket in half to save some weight. Now just stop and think about that for a second. If a pound and a half of extra blanket is that burdensome to merit chopping it in half, do you really thing your TES army feels like carrying around a pike, a longsword, and a shield and a crossbow on top of a suit of dwemer? Not likely. This brings me to another good point. Tents. Forget everything you've ever seen at a reenactment or in the movies. Big tents are heavy, difficult to dry and way to much effort to set up. Sure a general or a lord knight will get a spiffy tent, but by and large the PBI (Poor bloody infantry) will have to make due with shelter halves or even nothing at all.
On terrain: there is a good reason why the Spartans chose to battle the Persians in Thermopylae: narrow battlefield, hence no way of flanking.
Rough terrain - ever read a history book and been amazed how simple things always prove the biggest problem? The English army was nearly trapped in France during the Agincourt campaign because of a river. The French army at the same battle were massacred because a muddy field made it hard to ride horses. The Takeda army was destroyed by the Oda at Nagashino because of a bamboo fence. The Army of the Potomac was decimated at Fredericksburg because of a hill and a wall. Get the point? What is easy for one person to get by, alone is next to impossible for an army of thousands. This goes for forests, rivers, swamps, thick undergrowth, sand, mud, etc. There is a reason why battles are usually fought in big open fields and why armies like to march on roads.
On fatigue: have you ever tried to wield a heavy metallic sword for three straight hours? Well, I tried wielding a wooden sword for four minutes. And I was exhausted. So don't think anyone is able to go berserk for a whole day like Aragorn in LOTR. Sure, he's the hero, but the man hasn't slept for a month and he fights non-stop for two days at Helm's Deep. Two words - not realistic.
Fatigue - It's a universal rule throughout every army across the world and through time, everyone is tired. The TES world has certain things that we don't have in real life, fatigue potions for example. This will allow your TES armies to go just that bit farther when doing manual labor, marching, etc. However it is not a replacement for rest. Yes I know in the LOTR rings the orcs ran everywhere and never got tired. This is not LOTR, and you cannot do that. Nothing annoys other Rpers more than seeing a post saying that you've taken your army at a dead sprint, across difficult ground, through the woods and over a river to have them attack up a hill. People can't do that. Even if they could they would be in no shape for the grueling physical demands of battle.
On navy: a naval battle is like a chessplay. The one that has the wind in their backs, wins, because they have the propulsion to manouvre.
Navy - Naval battles are slow, painfully slow compared to land battles. They also usually have fairly simple tactics. This is a necessity because most ships are driven by wind. If you turn this way and that and dodge around, you'll usually spill the wind from your sails and be dead in the water until your crew can readjust. Also, ships are surprisingly difficult to sink. Almost everything on an old wooden ship will float. The usual outcome of a naval battle is that the ship is either captured or burns. At the battle of Trafalgar, one of the greatest naval battles of all time, only one ship actually sunk. The rest were, you guessed it, captured or burned.
Now onto fire. Fire is a ships worst enemy. They are basically giant floating matchboxes. Ships can catch fire with surprising ease. The ropes to the rigging are tarred, most planking is filled with tar and hemp fibers to make it waterproof. These things will burn if you look at them wrong. Very, very dangerous stuff.
On battlefield confusion: that's why most movie battles happen in the rain.
Battlefield confusion
As the name says, a battlefield is very confusing. There are a number of factors that come into play which cause problems. Noise and smoke are the two biggest. Noise, is rather obvious and wont be discussed. Smoke however can come from a number of different sources. Ever driven down a dirt road in a car or on a bike? You know that trail of dust kicked up? Imagine that coming from the feet of ten or twenty thousand guys. Unless it rained the day before a battle, your men will probably kick up at least some dirt. If you're in a desert, or in the middle of a dry spell, expect that dust to become a fog. This can cause men to be confused, to attack allies (Green on green) charge when they shouldn't or retreat if they're winning. Yes I know it'll hurt your cause if you portray this part in an RP. However, if you go about it in a mature fashion, it brings a ton of interest and character to the RP.