So in the south, I've taken out the Thessalian league, as well as the Tyrants of Pharae. My next plan is to sweep down to the Arcanian league and work my way up towards the coast, taken out Eprius as well as Illyria and securing my back.

But first, I would like to have a strategic chokepoint in the south to prevent the Phocians from causing to much damage. I don't plan on going into the Peloponnese until later on in the game. Lamia seems like a good chokepoint to be able to defend against against the Phocians, since it guards the northern chokepoint of Thermopylae. So I'm planning on taking that city and keeping a strong garrison there.

My question is, how would you go about sieging the city? I've scouted there a few times, and they've already begun massing TONS of units, I believe atleast 3-5 hoplite brigades from there own city. As well as a couple from their nearby cities. So they definitely won't be giving up the city without a fight. Since I'm able to go into Lamia through two paths, I'm thinking about sending my phalagites, peltasts, and catapults through one way, while I send my calvary around the other way, and try to flank them and make the battle easier. Of course, the two heroic shrines nearby don't help me either, but there's nothing I can do about that. Either way, this is probably going to be my hardest battle yet.

Here is my battle composition, if there's anything you'd recommend to add to help my side would be greatly appreciated :D.

Two Phalangite Brigades

Hypaspists

One Allied Hoplite Brigade

Four catapult batteries

Two peltast units

Companion Cavalry

One Allied Thessalian cavalry

One scout cavalry (don't really plan on using this one in battle, mainly just to catch defeated enemies for slaves)

I have plenty of recruits, as well as a substantial amount of gold, so anything within reason I could add to my attack force. Thanks for reading!

I would suggest 1-2 more phalanxes. At least two to block the western approach, 1-2 to block the east, and one to block the mountain pass to the north. You can sub in the Hypaspists for one of these. I recommend stationing the east and north ones out of range of the city. Advance from the west so that your catapults can attack the city but the city can't shoot your phalanxes. Then draw out the majority of the garrison to the west. Have your phalanxes lined up properly (no overcrowded penalty) with as many catapults and peltasts you can fit right behind them.

It's still going to be ugly, due to the heroic shrines and the natural high morale/combat ability Phocian hoplites have. You're probably not going to be able to get cavalry to work for flanking, as if you run a unit behind the enemy on the west more will come out of the city and chop them up.

The only other thing I would add is that you may want to look into getting the Agrianian peltasts. They're really good (and a fun change of pace from hoplite+cav hammer and anvil tactics). If you don't have them yet, explore to the east of the Northmost Paeonian cities to discover the objective.

That is not what I would do at all, but that doesn't mean anything. I would rather hold out in the southernmost Pheraean cities with 2 brigades of phalangites, and go to the north first. Once your entire Illyrian force is free to pressure other factions, try bringing them south to Acarnania and pressure the Phocians from two sides. Their main defense force will not go out on a raid, and if they do, you'll be able to stall them with two units until reinforcements arrive.

If you really want to attack them, try catching their melee units with your melee units, and running around them with cavalry to get the heroic shrines, at least one of them should be yours so their advantage is negated. There is nothing more devastating to an army with only 3 main battleline troops than 30 phalangites routing.
And thinking of that: The AI does not get the overcrowded modifier, so having the AI actually form a battleline and taking them one-on-one is way better than the big meatpile they usually form when defending. Couple that with the heroic shrines, and sometimes even generals, and they may massacre one of your units quite quickly. Try using the hypaspists as a damage sponge if that happens, even though they are your best troops.
Don't go in with your generals in the first rank. Seriously, don't! Make them stick to the back by rotating and rearranging your brigade until they do. Generals cannot die while attached to brigades, and they have less reach than phalangites, so they storm into the bulk of the enemy hoplites and get their brigade in the back massacred without anyone touching them.

Thanks GiftGrun. I'll probably go up into Illyria and secure my western front before going south. I was really on the edge about doing this because of the reasons you stated. Now I'm sure of what to do.

I'll probably leave a few phalangite units there, with the rest being allied hoplites to defend against any raids they attempt to send.

Also, thanks Alexander, I'll definitely use your strategy once I finish off much of the west, and more than likely by that time I'll have more money and troops to go into battle.