As part of the Spartan Empire, there's a long chain of boats allowing one-turn transport along most areas in the southern waters. Despite the fact it is rarely used, it nevertheless is worth the expense.
Because this network branches, I will just illustrate a single Journey.
King Agesipolis III of Sparta is travelling from Iberia (specifically, the Baleric Isles, where he has ended the Carthaginian threat) to the Eastern front, where the Seleucids are sieging Antiocheia. The chain actually can go even further down to the very capital of the Ptolemics... what does it look like?
This is what Agesipolis' trip might look like...
- Pollentia
- Sagunton
- Emporiae
- Massalia
- Arretium (or Aleria)
- Roma
- Capua
- Rhegion
- Crotona
- Olympia (or Thermoa)
- Sparte (Troop Pickup)
- Chalkis (or Athenai)
- Ephesos (or Halikarnassos)
- Rhodos
- Side
- Tarsos, Antiocheia or Laodikeia (endpoint)
- Ierosolyma
- Tanis
- Alexandria
Note: you can also take a branch to towards Pella, or even all the way to Crimea, or the western side of Armenia that is touching the water. Carthago and Sicily are also connected but the northern seas of Africa are not (you can go south from Carthago down to Lepcis Magna though)
Strategically speaking, my armies need only a few components:
- General
- Lancers (xystonphoroi hippeis or something): Anti-router
- Rhodian Slingers
- Pikemen
- Some infantry unit with spears
- Artillery
My lancers, Rhodian slingers and artillery are only obtainable from Sparte. I'm going to start using some Palmryan Pikemen, only obtainable (so far) in Antiochea. However, Sparte is the west-most settlement I have that trains Levy Pikemen.
The bulk of my losses are hoplites... thankfully any settlement can take two turns (I like to use ones with +XP and +armor/weapon upgrades) and be able to train the Ekdromoi light hoplites.
Note: Perioikoi Pikemen are a unit available anywhere at Tier 3 spartan barracks, and Greek Slingers are available at Tier 2 spartan barracks. But I prefer Levy pikemen (cheaper, sufficiently capable) and Rhodian slingers (more range, higher attack). I've tried using better hoplites, but once a few units are gone, and I start using Ekdromoi reinforcements it seems hardly worth the bother... I think you can also get Tarentines cavalry at Tier 2 barracks, there's no real reason I use the lancers (and they hardly kill anything but routers) but they are better at melee so I carry two units.
For most of the fighting in the East, there isn't much alternative to moving overland, so that could slow things down... Agesipolis is quite a monster though, with ancillaries and traits that give him huge amounts of +movement. He can drag siege engines much much further than a horse unit (without bonus) can move...
It's also possible to have boats just sitting in the water, allowing you to chain all the way from say Antiochia to the northern end of Cimbri territory... if not for pirates. But I don't think there are any around, and certainly no faction can raise a real navy.