Re: when should you build a new fortress?
 

With MA Ulm I think it is *important* to have more forts as fast as possible. Who cares if the capital has fewer resources at use, if you can build a 800 gp fort next to it and recruit an additional smith per turn sooner? More forts = more income and more resources = more smiths (and more knights too).

It is not like early game is too difficult for Ulm ever, is it? But it is so easy to fall behind in the research race as Ulm, and unless you have enough magic to stop the other players, you'll be just a road-bump when you meet another player. Still, it depends on the situation with Ulm too; best is IMO to look for spots with 800 gp forts and start a new one ASAP (as long as it does not mess up the smith producing in the other forts).

With other nations I tend to be much slower with building forts. Usually building first fort in a choke-point and/or something useful to recruit.

Re: when should you build a new fortress?
 

Thanks for all the answers guys. They will be of great help.

Re: when should you build a new fortress?
 

No. They do get spear and shield infantry, but they don't get longbowmen for the first 19. Instead they get millitia and slingers. The millitia have a moral of 8 and are as bad as millitia usually are. The slingers are even worse with a moral of 7. The book is slightly incorrect about what you get. It should read as follows:

Commander at def 1: Castellan
Units at def 1+: Spearmen, Millia, Slinger
Commander at def 20: Judge
Units at def 20+: Longbowmen, Tower Guard

Note: The tower guard you get is the version from MA Man, which is an inferior unit as it doesn't have a crossbow and uses a regular shield instead of the kite shield.

So, my point still stands. LA Man has terrible PD. They are better off using a castle instead.