Or he's trying to fight Northern Pagans
Yeah, those guys are strong at the start. I'll take Poland as an example since they border Pomeralia and the other 2 or 3 county Dukedoms (High chiefs as pagan in this version) to their north. Poland at the start, if you start as the king Boleslaw the Bold. If you declare holy war when the pagans are not distracted, they will all join the holy war in defense of their faith and form a relatively large stack of troops that can be about 5x what the whole kingdom of Poland can muster.
To beat them and take their lands (which Poland really needs as it's landlocked without) wait until the Holy Roman Empire declares holy war on them. Every time HRE declares holy war you should do the same on a different county or the same as the HRE if you want to steal counties from the HRE with their neutrality, though then you have to arrive first. The HRE is strong enough to win pretty easily after it's troops have consolidated. Once the Pagans have combined their own forces and are committed to losing that war, you have an opportunity to holy war the weaker pagan states. There will be a slight delay before other local pagans join in, so you can usually consolidate your army stack and put it in place before they try to dogpile you. If HRE has already crushed their main army usually you can siege the holdings in the county or duchy you are trying to holy war before they can reinforce enough to threaten you, but if you see an army that is sizeable that you can beat I would recommend chasing it down until there are no survivors.
After a while the pagans will not be able to muster as many as the start, and Poland can start grabbing as much land as possible, especially coastline, before Denmark, Sweden, the Russian principalities, and other Christians you can't holy war against take them.
You'll also want to be raising Crown laws when your ruler has been in power for a few years, and especially when they are about to die anyways. Raising Crown laws will make your
current vassals despise you, I think it's -40 which is really a large amount, and it lasts a really long time if not permanently. If you do it too early, you'll have a lot of faction rebellions throughout until the next generation of rulers is in place. I usually increase it to low if it's at the lowest with the first ruler, then go for free investiture as that will increase all the bishops' respect for you and they will often choose to pay you their taxes rather than Rome, and the Pope is the richest man in the world in most of my games thanks to those bishops across the world I think. A downside is the Pope will gladly excommunicate you at the request of vassals trying to form factions against you, and you'll have to send your chancellor to rome and hope he improves the Pope's opinion of you enough to accept your request to lift the execomunication, or pay a hefty Pope bribe if you can afford it on the intrigue list.
Once it's at High Crown authority, your armies will be very large as vassals are obligated to give you larger armies, your vassals will be angry, and I think, though I'm not sure, the decrease in relations for raising a vassal's armies accrue slower. In addition you can change the inheritence law to Primogeniture. That means you won't have to make non-primary male children into bishops or heirs to bishops anymore.
A note on making male dynasty members bishops to remove them from succession: make sure they are married to create more dynasty members before they attain the position. They will keep having children even after becoming a bishop. Since bishops do not pass their title to children and are instead appointed, they will become normal court members of the bishipric their father was previously in charge of once their bishop father dies. Since they are dynasty members with nothing important to do, they will often accept an invitation to your court, where you are in charge of their marriage and where they will be available to place as dukes or counties as you conquer territories.
A funny result though is that factions can form to turn one of the Bishops who are King's sons into the King. This results in a Theocracy if you accept their demands. I'm unsure if this would be beneficial in some situation; I haven't managed to attain an emperor level position yet as I usually start as Poland and that is right in the middle of no-empire. I'm focussing on trying to form Russia as Poland this game before the Mongols show up with their ridiculous no supply limit, though the hordes are unreplenishable until conquer penalty wears off their conquered territory. My previous game I ignored the Ilkhanate too long. I was watching them focus mostly on weakening the SouthEastern Islamic states when the Golden Horde's arrival surprised me. The Golden Horde decided to take the Teutonic Knight Catolic counties I had been requested to donate to the Knights after taking them from the Ilkhanate in a previous holy war of opportunity while they were busy far to the south. It was a free buffer state I could join the defensive wars of for opportunities to grind down the horde. The Golden Horde's largest doom stacks that ignore supply rules were destroyed in a defensive war by giving the HRE's somewhat youthful ruler one of my princesses for marriage to some relative of his own in exchange for an alliance. Shortly after that war, the Ilkhanate's conquer penalty for recruiting normal units wore off, and they were the largest nation in the world. The HRE was actually bordering Ilkhanate in a large HRE controlled Kingdom of Jerusalem that had expanded due to a fragmented Islamic world that lacked a large state that could counter a distant empire. HRE was losing all the wars they fought with Ilkhanate because of those darn no supply limit initial hordes trouncing the slow to consolidate HRE in 8k supply limit counties over and over while the Ilkhanate insta-siege holdings for 30 casualties with those same initially multiple 150k stacks that are not afraid to combine.
After the Teutonic Knights were pushed out by the Golden Horde, they relocated to another area that was taking some territory from Cumans or something. I took those back after the Golden Horde was more or less reduced to a normal realm by the destruction of it's horde armys as described previously, and the Ilkhanate declared war to take them back from me. I stacked everything I had and killed as many small forces as I could, then sat in a good defense county and let the hordes attack. I lost a good number of reloads due to being so badly outnumbered, but after a few the Great Khan was killed in one of those 'resists valiantly but was slain by our troops after being cornered' random popups and his child heir, who I had bribed a while back for 20 gold, inherits. Totally lucky; after that they never forced a reload by attacking me when I wasn't ready. I also kept my chanceller in the new Great Khans' court at all times after that since he already liked me and it seemed to work well. To keep him from getting mad at me, I only joined other's wars against him and if it was the HRE I'd try to consolidate with them despite the HRE AI screwing it up most of the time due to supply limits messing it up bad. If it wasn't the HRE I'd join the war to send armies off to the task of looting as many Ilkhanate holdings as possible in order to fund more army improving buildings. For instance, I donated a county that was in an Ilkhanate dominated duchy to the Catholic Pope so he could do something useful. It survived a while under Rome mostly because the Ilkhanate was busy down south. I did get to see some Popestacks fighting Khanstacks though.
That was about where I stopped playing that and lost the save file, and after a hiatus I'm doing another Poland Boleslaw game to try to form Russia before Mongols arrive.
One thing that I think would be cool to have in the game and would like to see added is being able to combine two adjacent Kingdoms a character is holder of into Empires if there are enough holdings or something like that within it. Poland is hard partly because it can't form some sort of Empire; that extra rank is a nice boost in diplomacy. It's really easy as Poland to eventually become King of Poland, then Lithuania through conquering it, and then Hungry through marriage of your heir to the King of Hungry's first daughter and some male heir slaying. All that territory combined is very large and can muster a lot of troops (top 5 in the Christian world easily) after a few generations of Crown law increase, but all of it is in the black zone on empire view. I think it could use some kind of Empire title, especially if it was possible through mechanics to make non-historical empires of multiple bordering Kingdoms you control. If it was an automatically named Empire depending on it's components, culture and religion that would be cool. If that gets too wordy maybe it could allow players to name the new Empire in the way the DF names are made, by choosing appropriate words for the Religion of the Emperer, and from a list of words from the cultures and religions. It would be cool if this was in addition to the the historical empires already in place, so you had the option to do either.
http://en.wikipedia.org/wiki/Polish%E2%80%93Lithuanian_Commonwealth+
except feudal elective as it's too early I guess for noble electorate, though maybe a nice bonus for those with the Republic city state DLC would be you could form an even earlier Polish-Lithuanian Commonwealth if were to turn Poland into a Republic however you do that (I don't have any expansions yet) and play well enough.
From wikipedia:
In Poland, after the death of the last Piast in 1370, Polish kings were initially elected by a small council; gradually, this privilege was granted to all members of the szlachta (Polish nobility). Kings of Poland and Grand Princes of Lithuania during the times of the Polish-Lithuanian Commonwealth (1569–1795) were elected by gatherings of crowds of nobles at a field in Wola, today a neighbourhood of Warsaw. Since in Poland all sons of a noble were nobles, and not only the eldest, every one of an estimated 500,000 nobles could potentially have participated in such elections in person - by far the widest franchise of any European country at the time. During the election period, the function of the king was performed by an interrex (usually in person of the primate of Poland). This unique Polish election was termed the free election (wolna elekcja).
(Boleslaw the Bold has excellent stats but is married to an average wife, it used to be he started unmarried but that made it easy to marry Matilda with him. To get Matilda you have to start as his brother who is in poor health, and then to take Poland you have to kill Boleslaw's children or wives until you can assassinate Boleslaw himself or somehow convince people to join your faction to depose him. It's difficult to do since Boleslaw's brother is pretty terrible, so if you'd like to play as Piasts it's a good idea to start as Boleslaw the Bold and then plot to kill your wife so you can remarry either a genius, a claimant on Russian lands, or best of all Matilda or another foreighn ruler of duke or better if she hasn't produced a male heir yet and her husband is killable through plots. After that kill all the dukes you can slay before they produce heirs (king is their heir) and pretty soon you will control the entirety of Poland. If you let your bumbling brother, poor health and all survive his inevitable attempts to faction against you he might produce children if you marry him to a lady with fertility bonus, and the quicker you expand your dynasty to have Piasts in charge in your realm the better, as initially it is composed of 3 surviving members, one of which is a woman married to a German duke, and two males with one being in poor health at the very start and who usually quickly becomes infirm or incapable with death shortly after.)