I would say go for 2-1 or 3-1 odds when assaulting a defensible position. Goblins would need to feel they vastly outnumber the town to even considering attacking. Because of the wall, and the fact they are goblins. I would suggest 3-1 or 4-1 odds. We faced 5 to 1 odds in a town of 5000 and managed to win, barely. But about half of that number were actual troops. We were level 6 at the time if it matters.

So I decided to draft some of the simpler rules and concepts I would like to use. It's all subject to overhaul at any time once I find better ideas. And there's lots and lots of detail.

Any ideas instead of the Casualty Count system? I hate the name. But I didn't want to use HP, so opted for a smaller set of concrete statuses. Of course, this does mean all armies have 5CC at most. How would I differentiate between drastically more powerful armies? Powers that give "damage reduction?" Ugh, yeah, needs an overhaul.

COMMANDING TROOPS

Troop command will come into play when the PCs reach 8th level.

Rules

The war is best played with a nice big map, allowing the use of miniatures (Risk pieces, Warhammer, minis, etc) to symbolize the location of armies. Otherwise, this is a big headache. Some book-keeping is still involved.

ARMIES
Each army signifies a certain number of soldiers, symbolized by one mini on the map. The cutoff for one army piece depends entirely on your campaign. I use 500 soldiers per army. Armies act as simplified swarms, moving according to their speed and launching attacks according to their powers and damage. Armies in battle accumulate casualties, growing weaker and weaker until they are eradicated.

ARMY HEALTH
Armies can sustain a certain number of casualties before their effectiveness begins to wane. These casualties are abstracted using their Casualty Count. Being at different Counts signifies different statuses for an army, summarized below:
0 CC: Perfect condition.
1 CC: Minor casualties, -1 to any attacks made by the army.
2 CC: Major casualties, -1 to AC.
3 CC: Devastated, cannot use any powers except Basic Attack or Final Charge.
4 CC: Scattered, army is lost. 50% of recovering 1CC for adjacent army or city.
5 CC: Eradicated, army is lost.

ARMY COMBAT
Combat is performed similarly to the character scale, but over a course of days.
Step 1: Detection. Armies in the same location roll opposing Perception and Stealth checks to spot/avoid one another. Hidden armies can opt out of combat, but must reroll the Stealth check every day. Hidden armies can also ambush flat-footed armies.
Step 2: Ambush (optional). Armies capable of ambushing an enemy army do so. They get use of a free power with no enemy counterattack.
Step 3: Initiative rolled. Both armies roll initiative to determine who is first to act.
Step 4: Army Combat. In initiative order, armies can use one power each. Repeat step 4 until combat is resolved or an army retreats.

Standard Army
Five hundred soldiers march forward, inching closer and closer to battle. Swordsmen, spearmen, archers, and even a few horses. The majority of the soldiers are human, though a few elves and eladrin are visible in the crowd.
Casualty Count: 0
Armor Class: 12
Initiative: +4
Speed: 20 miles/day
Skills: Perception +6, Stealth +2
Basic Attack: +4 vs. AC, a successful hit inflicts 1 Casualty Count on the target army.
Fearless Charge: +6 vs. AC, a successful hit inflicts 2 Casualty Counts on the target army. Whether the charge hits or not, this army gains 1 Casualty Count.
Retreat: Army moves its speed.
Special Units: None.

Dwarven Army
Marching to the beat of war drums, the dwarves are slow but immovable.
Casualty Count: 0
Armor Class: 16
Initiative: +0
Speed: 15 miles/day
Skills: Perception +4, Stealth +0
Basic Attack: +6 vs. AC, a successful hit inflicts 1 Casualty Count on the target army.
Defensive Phalanx: +2 vs. AC, a successful hit inflicts 1 Casualty Count on the target army, and the dwarven army gains +1 AC until the end of the next day.
Fearless Charge: +8 vs. AC, a successful hit inflicts 2 Casualty Counts on the target army. Whether the charge hits or not, this army gains 1 Casualty Count.
Retreat: Army moves its speed.
Special Units: None.

CITIES
Most cities have defensive qualities, and are often the site of conflict in battle. Cities above a certain population usually have token armies known as “militias.” Militias are not normally as strong as regular armies, but they make city-sacking more difficult. Cities can have fortifications that bestow bonuses to armies within them.

SPECIAL UNITS
Armies and stacks can have special units that bestow specific bonuses: speed, attack, powers, damage, and so on. Clerics and mages are the most common special units, along with officers and heroes.

That looks quite interesting...

But I think that by making the army (that is to say, the combination of all your "Swordsmen, spearmen, archers, and even a few horses"), you're depriving the game of, if not strategy, then at least of tactics. Treating the armies as swarms works, I guess, but I'd have gone for a slightly more complex system.

What I'm envisioning, would be the existence of two different "modes", one strategic and one tactical. The strategic one would simply be your risk-like map. In this mode, your armies would be moving, making abovementioned spot checks, and so forth.

If armies enter combat, they'd enter tactical mode. Each army'd be composed of platoons, consisting of 100 soldiers each. You'd treat each platoon like a swarm, and use your CC system to measure damage to them. There'd be different types of platoons, of course, such as swordsmen, spearmen, archers, cavalry, and specialty platoons. The specialty platoons (such as casters or grenadiers) would have certain combat abilities, but they'd also be able to do stuff in strategic mode. Each type of platoon would have different speed, Initiative, AC, abilities (Pikers could use "stand ground", to counter cavalry attacks, while archers could use "covering fire"). Platoons could also possess leaders, who'd give them additional combat bonuses.

This'd make the battles more complex of course, since there'd be a lot of platoons on the field, but the fact that players could play around with an army's composition, lead platoons themselves, and in general would have a bit more control over battles would make it pretty fun, I guess.

But anyway, do with that what you will. Re-reading it, I realize I borrowed a lot from the Heroes of Might and Magic series.

I would have to say, in addition to the CC rating you have, you should also allow the possibility of divisions retreating. Say you have 6 divisions fighting on the western flank. 2 divisions fall in a charge. There should be a chance the divisions fighting beside them can waver and retreat.

Krogoth, I think that would be the equivalent of just the retreat power given whatever health an army is at. Damaged armies (which are essentially CCs + special units when you break it down) could merge with/heal other armies.

No, you are right. This is like the "v0.1 Alpha" so it begins necessarily complex. I'm not sure if I want to make two different but almost identical "modes" - perhaps a similar effect can be generated by having special units, or I'll just change how armies are treated entirely.

I like the tactical mode thing, so I'm going to use that going forward.

Well, retreat seems to be a choice. Where as I guess I should have meant Fleeing. As in, they are morally screwed that they just want to get the hell out of there.

An implementation of Morale and Leadership bonuses would also have to be implemented.

As morale runs lower, more people would want to flee the battle scene, giving a boost to leadership if the generals in charge are veterans.

Something like that. Basically, how I view it, morale is the troop bonuses as a battle waxes and wanes. Leadership is an initial bonus that affects how troops fight, crits, etc.

Morale is interesting... though question is, how'd it be measured and implemented? I don't think it'd necessarily have to be bonuses. Leadership, yes, but I thought morale might affect the frequency with which troops act.

What I envision is this:
Morale is affected both by global and by local events. A positive global event can be an enemy platoon being destroyed, or an enemy leader being killed, a negative global event would be your side losing a platoon or a leader. Local events would simply be damage dealt and taken by a platoon, where more morale is gained for a particularly successful action. (That is to say, an attack by a platoon of swordsmen against an enemy specialty platoon, say, casters, would get more morale than if they attacked enemy pikers). Each event can add or subtract points from morale. Every platoon has a morale limit, both positive and negative. When the positive limit is reached, a unit either gets to act twice, gets combat bonuses for a while, or perhaps can use some sort of special combat technique. Up to you, really. When the negative limit is reached, the opposite happens, the unit becomes weaker, can't act, can only move for a turn, something along those lines. Different units can have different morale limits. Say, dwarven berserkers could have a fairly low positive limit, and a high negative limit, since they're already highly motivated. Units could also get morale bonuses or reductions at the start of a battle. Say, if an army is defending a holy city, their units'd start battle with a half-full morale gauge, if there's a bad omen, the entire army could start battle with negative morale.

It'd be complex, but not too badly so. You'd pretty much need a table for each platoon depicting damage, morale and leaders.

A thought occurs: why not just use the regular 4E battle system and multiply certain values by 10 or 100, depending on scale? You could still have a battlefield with a 1-inch grid, only one square would represent 50 feet instead of 5, or 500; accordingly, one miniature wouldn't be one guy but a squad of 10 or a batallion of 100.

And from there you just use all the usual values for hit points, defense, attacks etc. and treat every unit as a swarm (which as far as I can make out boils down to a damaging aura and certain resistances and vulnerabilities). Hit points, after all, are just a general "how well is this guy holding up" number and can represent almost anything. Units led by player characters could simply get the PC's stats and powers, or you could have the PCs as their own squad on the battlefield attacking gargantuan swarm enemies (maybe even tracking them on a regular-scaled map).

Morale bonus? The usual Intimidate mechanics. Liberally add +2 bonuses according to which side is doing well. The only slight problem I can immediately see is discrepancies between the range of powers in normal fights, where 10 squares are 50 feet, and on the battlefield, where they'd have to be 500 or even 5000. Maybe make something up about how the wizard's squad is made up from arcanists who are doing a little improptu ritualizing, and the archer's squad has a gigantic ballista.

The reasoning here is that 4e's battle system is pretty well thought out and balanced and I figure, why should I make up my own that might work when I can just as well slightly adapt the one that's there. Plus your players won't have to learn an entire new system.

You know what Meister, you've just taken all the fun out of this discussion by using the easy solution :( Now I am sad.

But what you do say does make sense. Although giving units the PC stats and powers is a bit of a stretch. If you have an rabble army of civilians, they aren't going to be able to fight at the same level as the PC. It could give them a bonus, but not the same stats. Sure you fight better with a competent leader, but not that much better.

I was thinking a bit about what the setting is and everything, but flanking would also have to have other side effects then bonuses to hit. I think it should affect morale. You could also use morale on a scale as well in which the other army might start reacting slower the more demoralized they get before out right retreating.