I was about to say something similar.

What I think is that there should ALWAYS be an option to retreat. How could there not be? When in battle and you choose to retreat, the different units should retreat toward the part of the map they are closest to. Also, the proximity each unit has to the enemy together with each units speed should determine the success rate of the retreat. (Horsemen can be closer than footmen, and flying units can retreat from almost right next to the enmy.) They take losses accordingly and we are back to the tactical map where the retreating army is spread around the battle. (Perhaps flying units should always be able to follow the commander/general)

It has always bugged me how retreat in other games has always seemed completly indifferent to the position of your army. If you have your whole army on one side of the map, and the enemy on the other side retreat should give you absolutly no losses. Instead most games just start number crunching or simply arbitrarily pick units that die.

Imagine if you want to retreat, you just don't press the retreat button. You start positioning your army, sacrificing units to hold off the enemy army. You have a bunch of pikemen on the wrong side of the map, well, they will be hunted down after the retreat, so insted of just running you send them at the enemy occuping them so your main force can gather up for a retreat. Your horsemen can propably get away in any direction so you use them to harass the enemy. Then when you are in position, your horsemen break of in each their direction and you sound the retreat.It makes the retreat very tactical, on both sides. Gives a whole new level to a battle.

Edit: This was supposed to be a reply to Levitages post. hmmmm... 

If the devs get one thing out of this thread, that has got to be it. There are plenty of ways to handle retreat well, but it largely depends on how combat is going to work. We are very much in the dark about the combat mechanics, so all of our ideas are almost more speculation than suggestion. But I think that almost regardless of the actual implementation they use, as long as it fulfills that one requirement, I think I'll be happy.

If retreating is available then multiple penalities should be associated such as:

1) When the retreat option is chosen 20% of all units must remain on the battlefield until the very end to provide a buffer so retreating units can escape.

2) Any units which have retreated should suffer a morale penalty of some kind.

3) A percentage of units which have retreated may not reappear for several turns since they remain hiding from the enemy army which forced the retreat.

4) Any siege weapons will be lost during a retreat since it's not possible to run away from an enemy while pulling a catapult or carrying a battering ram.

First having a catapult does not indicate they are sieging a castle... plenty of territory may need to be traveled on the way to the castle where the catapult can be ambushed / attacked.  Even if the catapult is at a castle then the people/beings inside the castle might be using other types of attacks other than melee to melee... such as their own catapults, longbowmen, or mages casting fireballs and disease.  I doubt very few engineers would try spending time pulling a catapult away when fireballs are flying across the battlefield and their general yells, "Retreat and Run for your lives!"

Only a few scenarios would provide an opportunity to retreat and still escape with siege weapons... those which involve beings within the castle under siege without any long range attacks.

And as within Age of Empires 2... there were scenarios where you knew there was no time to save those siege engines.  I estimate the best method would be if multiple retreat options exist during battle such as:

1) All Units Retreat as fast as you can leaving any heavy items and siege weapons behind.

2) All Units Retreat moving only as fast as the slowest unit leaving any heavy items and siege weapons behind.

3) All Units Retreat moving only as fast as the slowest unit which includes bringing any heavy items and siege weapons.  

yeah, but the whole point of a catapult is that you'd be outside the range of their bowmen.   Other catapults and mages are mostly valid, but a catapult generally is not accurate enough to something that isn't large (like a boat) and/or stationary (like a building).  You have augners and such that throw collections of stuff with the intention of hit many targets, but its rather short range.

 At a castle siege, they would be able to escape, so we can't have a case-all rule.   In Master of Magic, Civilizations, and such; rarely did battles that really called for a retreat included heavy slow warmachines that wern't at a town or casle siege.  Sure, they wouldn't be able to escape an ambush on the road, but most battles that I can imagine where a heavy long range war machine would be on the offensive, it would have room to escape provided the retreat was sounded before the warmachines were somehow on the front lines. (i.e. the battle was pushed back to where they were stationed)

Another scenario is the common hit-run tactic.   You have several large balistas, you engage a battle and snipe with the long-range war machines.  Its a retreat, but its not exactly 'run for your lives' as you used in your example.  Certainly the enemy is going to try to chase down the war machines, but its not like all of them are going to be found and lost.   Especially if retreating into a forest.  They could hide the balistas under bushes and escape into the woods.

Additionally, warmachines vs. warmachines would result in something again where either side could escape, but nobody is going to fight battering ram vs. battering ram.  They would do virtually no damage against units, so neither general would want to waste time fighting.

really that isn't the entire point anyway.  you didn't address the fact that the crew of the warmachines would escape.  So when people come to chase them down all they get are the machines themselves, but not the crew.  So even in an ambush with 0% chance the machine might be able to be moved, the machines might be destroyed, but can be rebuilt or repaired later.   It is the reason that in Heroes of Might and magic, you get the war machines come back after every battle, its not about the machine itself since that isn't the hard part of producing a catapult or battering ram.

I would vote there should be more factors then what you posted.   Such factors heavily involve against whom they are fighting and who is the aggressor.  If some guys are hauling a catapult through the woods and they are ambushed, heck yeah are they going to drop what they are doing and run screaming.

But if they are the attacking party, they are going to be able to be prepared to make a quick getaway dispite the large hard to move machine (like having cut branches or a cave or something back over the hill to hide)

I agree.   I think E:WaR should have something close to the AoW style retreat at best where you can run guys to the edge of the battle field to escape, so the catapults can run away many turns before the golem-tanks do (they still could have plenty of health and would be keeping persuers from reaching the catapults) then once all the weak and slow guys have gotten off, the golems can walk their armored bums away (or just die because they were taking all the heat as the rest of the army escaped)

I remember getting so frustrated in games where it was like "There is no way that I could lose another unit" then I hit the auto-battle, and the AI does something stupid and costs me a unit I shouldn't have lost (like running my ammo-less archers accross the field to fight an earth elemental when there are already 2 wyvern riders and a storm giant dealing it it)

No... because even during a castle siege it could be an ambush from the owner of the castle.  Where the owner has a few hundred gargoyles hidden against the inside of the walls.  Thus the war machines do not escape.

Yes they can be repaired later... but naturally this should cost not only time but resources.  Naturally the engineer cannot create another catapult and/or ballista in a desert full of sand.  It's not like the engineer waves a wand like some spell.  I do agree the engineers should be allowed to run away separately from the machine.

In Heroes of Might and Magic III...  the war machines such as the ballista, ammo cart and first aid tent were lost if destroyed at the end of each battle which is logically understood.  The catapult was automatically returned because it was the only device within the game to break walls besides one specific spell and each army could only carry one in the game.  I doubt we'll see the same limitations.

As I wrote earlier... just because someone is attacking does not mean a trap could not be waiting where a stronger and faster army is waiting in the shadows.  The attackers shouldn't be guaranteed to have any slow machine escape when the defender easily out matches them via speed and strength on the battlefield.

I like the AoW way (but I haven't played Dominions or Total War). Individual units retreat and only the attacker can retreat. This enables subtle strategies like engaging a big enemy force with fast scouts and pound the enemy with spells while most scouts retreat and a few run around to prolong the spellcasting.

Realism doesn't matter. Only what is FUN and works in the game should be considered!

Here's a simple rule that gamedevelopment should follow: "The gamemechanics that are fun and work in the context of the game will be what we use".

It did? I never noticed, perhaps my unis were always faster.. I started using the retreat option to scope out how man defenders were really in unowned nodes....

Hmmm, no speed differences between units on the strategic map??? That seems rather odd!

Too bad, a 'unit speed/% chance of success fleeing combat' would have been a good concept to implement.

The option to retreat is very important

I'd want a spell that might prevent fleeing.  It could be a high level spell, but still.  In HoMM I was always angry when I'd crush an enemy wizard down to like 1 unit then they would flee.  Sometimes I'd have such an overwhelming force that I couldn't imagine how they could escape.   

I still think that a percentage chance on losing retreating units (modified by the INDIVIDUAL speeds of your units and the enemy units) is the way to go!