I love history lessons and that's partly what I was looking for, which is why I went here instead of Rules. I was kind of hoping someone's search-fu was better than mine when it comes to the armies though and numbers specific to Pathfinder. I also checked UC under the Kingdom Building but didn't see it either.
One thing though that helped clarify nobles is a point that both DM Dubs and Questor hit on. So you start at the king, who owns everything. he doles out land and titles to his children, extended family, and trusted vassals. He does this not 'cuz he's awesome, but because then his kids and family hold most of the lands and keep the line of succession going, and then the trusted vassals hopefully continue toeing the family line and don't revolt.
I sort of understood this, but then I could never rationalize landless nobles or noble-on-noble skirmishing. Now I'm starting to understand.
The point these 2 astute posters make is that sometimes in real life nobles get a title without land simply to give them legal and social rights not normally afforded, like being able to have commoners duel for them or not being persecuted for loitering or something.
Landed nobles might fight among themselves for like honor or something, but most of their disputes could be settled by marriages, shady deals or money. Why would any noble ever fight to acquire land though, if said land was doled out by a higher noble?
Well perhaps the landless noble chafes against the foolish count who got his lofty position and lands from just being born, but the landless baron saved the king's niece and an entire town from siege through brilliant tactics and bloody battle.
So knowing the king is ruthless and will honor him if he can pull it off, the baron uses his title's legal advantage to hire a mercenary army from the town he saved. He then storms the count's keep, manages to siege it and takes out the count. The king, in like fashion, hands over the former count's lands. However legally the count's hereditary title COULD go to the baron, or it COULD pass to the count's infant son who the nursemaid managed to escape with (potential plot hook?)
The reason none of this ever made sense to me was... WHO CARES about legal and social rights in a medieval fantasy roleplaying game? I just figured nobles equaled land in some way because when playing an RPG I'm looking at a giant hex map of sparsely populated land plagued by slavering hordes of pure evil.
Oh sure, when world building I'd pay lip service to legal issues like noting which court would prosecute and hang a PC for murder or whatever. It never occurred to me that nobles would care more about such courts and their rights than, say, a goblin horde working for an evil witch that can raise and command the dead.
In my games I'm a fan of non-hereditary merchant barons; folks with lots of money that buy their way into nobility and a chip on their shoulder because they don't hold land and can't pass the title on to their kin. I always just said though that they already built up a big business, made tons of money, and THEN bought the title.
It never occurred to me that I might have it backwards. Perhaps they scraped together just enough gold to dump it all on a title, that then afforded them the rights to OWN a business instead of just working for someone else. Then they re-built their fortunes steadily and might even own other side businesses.
As for the military numbers, I'll have to just wing it. There's a 1-100 ratio I use for guards INSIDE settlements, so I suppose I could just as easily guesstimate using that ratio applied to the relative size of a political area. Then I'll just toy with the numbers, like Baron Von Irongate is a war-monger so even though there's 5000 people in his lands he actually has like 750 soldiers, but the Earl of Gloomynmere is very poor and his lands are plagued by fey, so even with 6000 population he only commands 450 soldiers.