I sent this to someone to so they might try the demo and see if they like it:
I was running a polish dynasty but then I had too much fun with the third king because the foreign noble wife I married for her land was too ambitious and kept pissing me off so I fathered 4 kids with her so they could claim her lands for my dynasty, then once the last king was like 55 and the wife infertile at 45+ I took a lusty teenage mistress and fathered a bastard I named Bastard instead of the default polish name so I could find him easily. Anyways I assigned that bastard to be educated by the first wife and made her the court jester to top it all off. Meanwhile the king's deceased father's living mistress (who was also 50 years her first husband's junior and not the king's mother) I arranged to marry the king's 16 year old son, there-by making her the king's mother-inlaw and daughter-inlaw (and her own Grandma-inlaw) at the same time and also the mother of his half-sister who was fifteen years younger or so than the king was. The entire family disliked the asshole king who I was playing as at the time of his death except for his heir. The queen raised the bastard to be ambitious which is the worst trait in a vassal for obvious reasons and it was probably because she hated the king more than anything. The succession laws of the kingdom split all the holdings between the male offspring. Literally the day after the worst king ever finally died the entire family split into factions based around the male heirs and formed independent states and a massive succession war broke out that the legal successor had no chance of winning probably. Before that though I had all of Poland and Pomerania, all Poland's originally disputed territory, about 1/3 of Italy (through marriage and inheritance) and 1/4 of Sicily (through non pope sanctioned crusade on the last Muslim territory remaining on Sicily[basically stole the fuck out of it because that was ok back then]), the majority of Finland and some of Northwest Russia. The first King of Poland captured Acre and retreated safely back to Poland in the first Crusade before the Pope was foolish and sent his moderate sized armies one at a time at the giant army the Emirate of something (Muslims) managed to consolidate like the Pope should have. South Sicily's culture was changed to Polish after I brought in a bunch of young men to start families there, and the predominate religion was changed to Catholic from Sunni Muslim after I had the Polish head priest run an Inquisition for a decade or so. I did that to a bunch of pagan states in Northern Europe too but it's a slow process. Basically I screwed up that dynasty by not giving out land carefully and making sure I consolidate my holding in a few counties so I can focus my investments and return. I think I'll start as an Irish noble next because I've heard on B12 that Irish starts are difficult since you start as a single County rather than a whole kingdom of multiple counties like I did as the Polish King. I think I'll finish the Polish game first and enjoy the mayhem and bloodshed caused by feudal relations and see if I can re-unite the territory once the Ai stops arresting or killing my characters.
Also before I made them stop fighting by passing crown authority laws I somehow caused a catastrophe inadvertently and caused a feudal civil war between two of my vassals when I was trying to be generous and hand out titles. One was a 10 year old countess and the other was her father. The father declared war and smashed her holding's armies, then sieged and took the countess prisoner. Then he had her executed. It's probably sort of a bug but it was pretty messed up once I figured it out. I established more crown authority so there weren't any more interior squabbles after that except for rebellion.
If you start in 1066, as the Polish Piast dynasty marry Matilda immediately. It's like getting a third of Italy for free for your successor. It probably works for other rulers too.
It seems the first crusade tends to be called around 1080 and the crusaders don't consolidate well. They don't combine forces and the Muslims manage to put together an army 10-25k while the individual kingdoms of Europe send all the army they can muster (around 3k-8k or so) and don't coordinate well, meaning the giant army destroys the smaller ones one at a time. As a moderate power like Poland the best you can do is hire mercs and consolidate everything you have and try to stay near a large army. Due to attrition you can't stay right on top of the largest and the giant Muslim army will find your smaller force and usually catch it. The early Crusade (pre-holy orders) could use better coordination between rulers of kingdoms and the pope. It seems like the problem is that the Muslim ruler can just combine all his armies and make an enormous force while the kingdoms of Europe have trouble combining their force and the only hope is the player being able to make a 10-20k army themselves (which requires starting as an emperor maybe) or saving your pillage loot solely for mercenaries. You'd be fighting attrition from supply to do so as well, which is cool but when the AI shows no strategy and moves the army you are shadowing in the hope that it will be there to move onto if a huge army tries to move towards you to impossible locations and leaves you to be picked off by the larger enemy army it makes me save scum as the ai is un-influenceable.
'Sir, the Polish army is retreating away from a large Muslim force toward this county we are in that can only barely feed both armies. Together we are slightly more than the Muslims and might win.'
'Let's march away from that and into the desert because there is a castle there I was going to siege.'
What can happen is that army moves there, if the Polish army moves onto it the Muslim army sits and waits for attrition to weaken the army. The only way to not personally lose is to retreat as soon as you notice you risk being stomped by the large army. It would be nice to have some sort of notification sent to the player where to consolidate and what the general plan is relating to the available forces. An example would be Mount & Blade sieges; the vassals all pick someone to listen to and the player while still independent has a sort of guideline as to where the armies should be to allow a reasonable concentration of force. If the participants could receive letters of strategy from the Pope regarding where to consolidate that would help a lot I think as well as armies in the same crusade/jihad supporting each other a bit better regarding local allied armies.
I think I saw an option somewhere to follow an allied army but I haven't tried it yet. If that respects supply and attrition that would be the solution. For example if I set an 8k army to follow a 10k army, if the 10k army moves into a county that supports 11k, it would be cool if it could split the armies until it's just under 11k and leave the rest in the previous county, then if needed move to reinforce the previous county's remaining army immediately if the enemy attacks it.