leo
Knight

The difficulty of advancing a unit from one stage to the next is determined by the unit's level at the time; the level of the unit that is being advanced to is irrelevant. IE, swadian crossbowmen are level 14 and they advance to being swadian sharpshooters, which are level 24. In this case, 14 is the relevant number for advancement.
In general, the rule is as follows:
The higher level a given unit is, the more experience it will take for it to advance to the next stage.
Now for some fun with numbers!
The previously mentioned Swadian Crossbowmen (Level 14) are the easiest fourth tier unit in the game to advance to the next level. The hardest unit in the game to advance by one stage is the Dark Hunter, clocking in at a massive level 23.
Advancement path of manhunters (Name / Level):
Manhunter 10
Slave Driver 14
Slave Hunter 18
Slave Crusher 22
Slaver Chief 26
[Whoa. Manhunters are the single hardest unit in the game to advance from their first tier (the basic manhunter) all the way to the final unit. This is crazy.]
Advancement path for refugees:
Refugee 1
Follower Woman 5
Fighter Woman 10
Hunter Woman 16
Sword Sister 22
[Mmm, this is an easy path! Nice and fast. Refugees are the single easiest unit in the game to advance one tier.]
Swadian peasant advancement paths:
(To Sharpshooter):
Swadian Peasant 4
Swadian Militia 9
Swadian Skirmisher 14
Swadian Crossbowman 14
Swadian Sharpshooter 24
[I think something is broken about the crossbowman's level. It's exactly identical to the level of the skirmisher, and because the level is so low, it's extremely easy to advance a crossbowman to sharpshooter.]
(To Sergeant)
Swadian Peasant 4
Swadian Militia 9
Swadian Footman 14
Swadian Infantry 20
Swadian Seargent 25
[Whoa, those level twenty infantry are hard to advance.]
(To swadian knight)
Swadian Peasant 4
Swadian Militia 9
Swadian Footman 14
Swadian Man-At-Arms 20
Swadian Knight 25
[It's exactly as difficult to raise a knight as it is to raise a sergeant.]
Vaegir Peasant Advancement Paths:
(To Marksman)
Vaegir Peasant 4
Vaegir Footman 9
Vaegir Skirmisher 14
Vaegir Archer 19
Vaegir Marksman 24
[It's much harder to raise an archer to marksman than it is to raise a crossbowman to sharpshooter.
]
(To Guard)
Vaegir Peasant 4
Vaegir Footman 9
Vaegir Veteran 14
Vaegir Infantry 19
Vaegir Guard 24
[It's slightly easier to get a Vaegir Guard than it is to get a Swadian Sergeant because Vaegir infantry are level 19 and Swadian infantry are level 20.]
(To Knight)
Vaegir Peasant 4
Vaegir Footman 9
Vaegir Veteran 14
Vaegir Horseman 19
Vaegir Knight 24
[Like with infantry, it's slightly easier to get a Vaegir Knight than it is to get a Swadian Knight.]
Zendar Townsman Advancement Path:
Townsman/Peasant 4
Watchman 9
Caravan Guard 14, Sea Raider 16
Mercenary 20
Hired Blade 20
[An interesting point to note is that sea raiders are harder to raise to mercenary status than caravan guards are. Otherwise, this is a fairly normal advancement path.]
Other weirdness:
Dark Hunters are level 23, which makes them the single hardest unit to advance.
The river pirate --> bandit --> brigand path is extremely fast, but brigands suck compared to other terminal units and bandits are hard to get a hold of anyways.
Conclusions:
If you're morally flexible, the easiest ranged units to obtain are Swadian Sharpshooters-- it is way easier to get a Sharpshooter than a Marksman-- and the easiest high-tier infantry and knights come from the Vaegirs.
Manhunters are a huge pain to level up, and a pretty worthless unit (and difficult to get anyways), so I highly recommend not bothering with them.[/b]
In general, the rule is as follows:
The higher level a given unit is, the more experience it will take for it to advance to the next stage.
Now for some fun with numbers!
The previously mentioned Swadian Crossbowmen (Level 14) are the easiest fourth tier unit in the game to advance to the next level. The hardest unit in the game to advance by one stage is the Dark Hunter, clocking in at a massive level 23.
Advancement path of manhunters (Name / Level):
Manhunter 10
Slave Driver 14
Slave Hunter 18
Slave Crusher 22
Slaver Chief 26
[Whoa. Manhunters are the single hardest unit in the game to advance from their first tier (the basic manhunter) all the way to the final unit. This is crazy.]
Advancement path for refugees:
Refugee 1
Follower Woman 5
Fighter Woman 10
Hunter Woman 16
Sword Sister 22
[Mmm, this is an easy path! Nice and fast. Refugees are the single easiest unit in the game to advance one tier.]
Swadian peasant advancement paths:
(To Sharpshooter):
Swadian Peasant 4
Swadian Militia 9
Swadian Skirmisher 14
Swadian Crossbowman 14
Swadian Sharpshooter 24
[I think something is broken about the crossbowman's level. It's exactly identical to the level of the skirmisher, and because the level is so low, it's extremely easy to advance a crossbowman to sharpshooter.]
(To Sergeant)
Swadian Peasant 4
Swadian Militia 9
Swadian Footman 14
Swadian Infantry 20
Swadian Seargent 25
[Whoa, those level twenty infantry are hard to advance.]
(To swadian knight)
Swadian Peasant 4
Swadian Militia 9
Swadian Footman 14
Swadian Man-At-Arms 20
Swadian Knight 25
[It's exactly as difficult to raise a knight as it is to raise a sergeant.]
Vaegir Peasant Advancement Paths:
(To Marksman)
Vaegir Peasant 4
Vaegir Footman 9
Vaegir Skirmisher 14
Vaegir Archer 19
Vaegir Marksman 24
[It's much harder to raise an archer to marksman than it is to raise a crossbowman to sharpshooter.
(To Guard)
Vaegir Peasant 4
Vaegir Footman 9
Vaegir Veteran 14
Vaegir Infantry 19
Vaegir Guard 24
[It's slightly easier to get a Vaegir Guard than it is to get a Swadian Sergeant because Vaegir infantry are level 19 and Swadian infantry are level 20.]
(To Knight)
Vaegir Peasant 4
Vaegir Footman 9
Vaegir Veteran 14
Vaegir Horseman 19
Vaegir Knight 24
[Like with infantry, it's slightly easier to get a Vaegir Knight than it is to get a Swadian Knight.]
Zendar Townsman Advancement Path:
Townsman/Peasant 4
Watchman 9
Caravan Guard 14, Sea Raider 16
Mercenary 20
Hired Blade 20
[An interesting point to note is that sea raiders are harder to raise to mercenary status than caravan guards are. Otherwise, this is a fairly normal advancement path.]
Other weirdness:
Dark Hunters are level 23, which makes them the single hardest unit to advance.
The river pirate --> bandit --> brigand path is extremely fast, but brigands suck compared to other terminal units and bandits are hard to get a hold of anyways.
Conclusions:
If you're morally flexible, the easiest ranged units to obtain are Swadian Sharpshooters-- it is way easier to get a Sharpshooter than a Marksman-- and the easiest high-tier infantry and knights come from the Vaegirs.
Manhunters are a huge pain to level up, and a pretty worthless unit (and difficult to get anyways), so I highly recommend not bothering with them.[/b]