Crusader Kings II

[El Guapo]

It will matter more once you form the Kingdom of Ireland and can then hand out Duke titles.

If you make someone a count in a duchy but do not grant them the respective Duke title, they will get a -25 relations penalty with you (if you look at their relationship will you, the modifiers will include "-25 desires duchy of [name]". Obviously the more the vassal dislikes you, the more likely they are to rebel, support factions, plot against you, and the fewer troops they will give you when called upon.

So when you're king it's generally better to keep your personal demesne limited to your retained Duke title(s). Not sure how close you are to creating Ireland, but you may want to think about that in advance when dividing up counties.

[El Guapo]

That's a question with a potentially very complicated answer. At it's most simple level, you're going to want to hold two duchies for yourself (IIRC, it's been a few months since I played last), and you want to make sure you control all the counties in those duchies. The reason you want to do this is because a count under a duke will want the duchy for himself, and will begin to resent the current duke. You don't want that duke to be you. For that reason, it's best to just isolate yourself from any such squabbles.

The best approach to dividing duchies and counties between yourself and your vassals is to do what I mentioned above, then make sure that you give the excess duchies to family members if possible. But here's the trick: The new duke doesn't have to actually own a county in that duchy in order to be duke there. You can really take advantage of this. Instead of having these counts direct their hate towards you, you make them hate the guy you gave the duchy to, and he will have few ways to deal with this problem. The more divided your vassals are, the less likely they are to be able to arrange powerful factions against you. Divide and conquer. Just make sure your vassals aren't allowed to fight each other, or you risk having large civil wars break out in your lands.

You technically don't get an advantage by keeping all the counties in your own duchies, but you do avoid some pretty serious disadvantages, and by being a little shrewd you can even turn the disadvantages to your own advantage.

Note that you *can* still have civil wars even if vassal infighting is forbidden, insofar as a count can rebel against his Lord and try to take one of his Duke titles. The vassal infighting prohibition that comes with Medium Crown Authority just prevents war between otherwise independent vassals, and not internal rebellions.

[Cortilian]

Thanks a bunch Tilt. That does help. One more question.

Is there a way to swap county ownership around without REALLY pissing people off? Example: I want to control all the counties in the duchy of Munster but one of them has been given to my brother by me. Can I just swap him control to another county and take over his without him putting a snake in my bed?

Thanks also El Guapo. I have created the Kingdom of Ireland and county ownership looks like quilt. Its a mess and people are pissed. Thanks for the advice,

[El Guapo]

Thanks a bunch Tilt. That does help. One more question.

Is there a way to swap county ownership around without REALLY pissing people off? Example: I want to control all the counties in the duchy of Munster but one of them has been given to my brother by me. Can I just swap him control to another county and take over his without him putting a snake in my bed?

No. There is no "trading" titles, so you would have to revoke respective titles and hand them out again.

On top of that, revoking a title is going to piss off all your other vassals too (because if you can take his title then you can take theirs too). The only way you avoid the other vassal penalty is if you have a good reason for taking the title (either you have a personal claim to the county, the vassal has rebelled against you, the vassal has a discovered plot against you, or the vassal is a heretic (if you have at least Medium Crown Authority). But that will still piss off your brother (and may cause him to rebel against you).

As the King of Sweden I got a sweet reorganization help when I saw that one of my Dukes with better counties had adopted a heresy (a Catholicism offshoot). Got to strip all of his titles without any difficulty and handed out my lesser counties to other people. Really handy - I just wish there was some way to try to persuade less favored vassals to switch to paganism or something.

[TiLT]

If you make someone a count in a duchy but do not grant them the respective Duke title, they will get a -25 relations penalty with you (if you look at their relationship will you, the modifiers will include "-25 desires duchy of [name]".

For the record, this only applies if you hold the duke title personally. If you give it to someone else, they will receive that penalty instead of you. As a bonus, the one you give the duchy to will love you for it, even if it's a poisoned gift.

Is there a way to swap county ownership around without REALLY pissing people off?

No. Trying to manage titles is the core of Crusader Kings 2, and figuring out how to do this properly is what the game is about, to a large extent. You need to plan in advance so that the titles end up where you want them, and if they end up in a different place (which happens all the time), you have to figure out a way to get the title back under your control.

There's lots of ways of doing that, of course, but the two most common ways of getting a title back from someone are:

1) Wait for them to rebel (or provoke them), at which point you can defeat them and take away any one of their titles without incurring any penalties.
2) Eradicate their line of inheritance so that when the current title holder dies, you'll inherit his titles (as his lord. This requires him to be your direct vassal). Then kill him (subtly) or let time be your ally. Some of my most memorable CK2 moments have emerged from this strategy.

Of course, you can always just strip titles from anyone you like, but you'll have to deal with the consequences.

[El Guapo]

Really wish I could just leave a Q'uran or two lying around the castles of unwanted vassals.

[El Guapo]

I was just about to conclude a successful Holy War in Karelia, when the pagan duke (high chief) went and converted to Christianity, which brought my holy war to an abrupt halt. What a jerk!

[TiLT]

Yeah, that kind of thing happens all the time in this game, especially when it comes to the death of rulers. Nothing beats the feeling of being about to win a major war, only to have the entire thing canceled because circumstances change beyond your control (like the claimant dying).

[El Guapo]

I mean, it's still a two-county state at this point with a demolished army versus my Kingdom of Sweden + Finland, so it's not a major drag. The only issue at this point is whether I press the claim of a Finnish courtier for Karelia (which would give me control over Karelia, but with a Finnish duke) or whether I fight two de jure wars for the two counties, which would take more time but allow me to put a Duke in place that is of my culture (and so who would like me more).

[Doomboy]

I decided to start a game as a Jewish merchant in one of the republics. I switched the character over to Jewish, gave him some nice traits, started a game up, invited a bunch of other Jewish people to court so I wouldn't have a bunch of people hating me to rely on. But I can't seem to get married. Is this a bug or something? None of the Jewish girls I invited to court are interested in getting married!

I could start over with a wife, I suppose, but then I don't get to choose the best candidate. And then there is the whole potential problem with wasting hours of my time if my kids can't get married too!

Then again, maybe I am doing something wrong. Has anyone got any advice either way?

[TiLT]

That seems like a backwards way of doing it. You don't have to invite someone to your court to marry them. Just ask their liege lord for permission and the rest is automatic. There's even an entire tool in the game for finding good candidates for marriage, and seeing if their liege lord is willing to marry them off is very quick and straightforward.

[El Guapo]

That seems like a backwards way of doing it. You don't have to invite someone to your court to marry them. Just ask their liege lord for permission and the rest is automatic. There's even an entire tool in the game for finding good candidates for marriage, and seeing if their liege lord is willing to marry them off is very quick and straightforward.

I wish there was a "search" feature in a lot of the screening menus, though. I was trying to find a bride with the "lustful" trait (I needed an heir quick) - would've been much easier if I could bring up the candidates and then do a search for "lustful".

[Doomboy]

The problem isn't how I am looking for a bride. The problem is that I can't find any women to marry. I guess that is just the main problem with being Jewish, there aren't any Jewish women that I didn't create by inviting women to court.

For some reason I can't marry someone who is in my court, although I know I have done that previously as a catholic in a republic.

Unless I am doing something wrong about the marriage thing? I have done it all a bunch of times before, just never as a Jewish character. I even remember marrying one of my non-Jewish courtiers to a Jewish guy that came to my court one time. But playing as a Jew, I can't seem to make it happen.

I guess if I want to do this, I will have to start with a wife, and hope the bug doesn't replicate itself with my kids.

[El Guapo]

Try YeOldeJDate.com

[Holman]

Have you hired a Court Yenta?

[Doomboy]

I don't know what that is. So probably not.

[El Guapo]

Well, last night I finally completed the process of turning a Norwegian county (the County of Jemtland) into the Empire of Scandinavia, over the course of about a century and a half. Count of Jemtland --> Duke of Jemtland --> Duke of Uppland + Bergslagen --> King of Sweden --> King of Finland --> King of Norway --> Emperor of Scandinavia.

So....not sure what's next. I guess find someone who has a claim to the Danish throne and press it, which should make the new Danish King a vassal of the empire. Maybe another crusade (I did participate in the successful crusade for Andalusia, which was fun). Otherwise that's probably going to be it for the game, as I'm not sure there's another mountain to climb.

Also I enjoyed the recent papacy of Hilarius II.

[TiLT]

Don't you dare quit until the game forces you to! You may have that empire today, but you're going to lose it, or at least risk doing so, later. The most exciting war in my last campaign took place after I had established the empire of Britannia and a group of dissatisfied dukes and counts decided to start a succession war upon my ruler's death. It was the closest I ever came to losing everything I had, and I had to hire several groups of mercenaries. In the end I even ran out of money and had to fight my mercenaries, who had now changed sides.

I was surprisingly merciful towards the rebels afterwards. Hell, one of the instigators was my own brother, who got to keep all his titles (I think I even gave him another one) and his freedom. He was completely loyal towards me for the rest of his life.

[El Guapo]

Don't you dare quit until the game forces you to! You may have that empire today, but you're going to lose it, or at least risk doing so, later. The most exciting war in my last campaign took place after I had established the empire of Britannia and a group of dissatisfied dukes and counts decided to start a succession war upon my ruler's death. It was the closest I ever came to losing everything I had, and I had to hire several groups of mercenaries. In the end I even ran out of money and had to fight my mercenaries, who had now changed sides.

I was surprisingly merciful towards the rebels afterwards. Hell, one of the instigators was my own brother, who got to keep all his titles (I think I even gave him another one) and his freedom. He was completely loyal towards me for the rest of his life.

I'll definitely keep going for a bit at least - the Danish crown currently eludes me, for one. Denmark's no wuss either, as the King of Denmark is also the King of England, so they can muster a decent sized army (though I can outpace it at this point).

But interestingly I haven't really had any succession issues. For most of my history (up until I usurped the Norwegian crown) I had elective succession, which was a bit hairy at times (could've been disastrous given a death at the wrong time) but which was overall surprisingly easy to manage (I found that if I had a son, installed him as Duke and kept my vassals happy they were consistently fine with voting for my son to succeed me). And elective succession helped keep the vassals happy.

Though once I picked up Norway, which had Primogeniture succession, I decided to go ahead and move Sweden and Finland to that to keep everything together and in the family. I have only had one succession since then, which went unchallenged. My current wife is really cranking out the kids though - I think we're up to four, plus three kids from the ex wife (three sons and four daughters) so I guess there'll be a few potential contenders.

I should check if any of the younger sons have "ambitious" and if so ship them off to the Teutonic Order.

Also, one thing that I think is a nice touch is that Scotland is ruled in my game by a Norwegian dynasty (the King was King of Norway and Scotland before I usurped the former title), and so is labeled as "Skottland" in the game.

[El Guapo]

Don't you dare quit until the game forces you to! You may have that empire today, but you're going to lose it, or at least risk doing so, later. The most exciting war in my last campaign took place after I had established the empire of Britannia and a group of dissatisfied dukes and counts decided to start a succession war upon my ruler's death. It was the closest I ever came to losing everything I had, and I had to hire several groups of mercenaries. In the end I even ran out of money and had to fight my mercenaries, who had now changed sides.

I was surprisingly merciful towards the rebels afterwards. Hell, one of the instigators was my own brother, who got to keep all his titles (I think I even gave him another one) and his freedom. He was completely loyal towards me for the rest of his life.

Also you may be pleased to know that I have virtually wiped out Swedish culture in the game - there are maybe four or five counties left in the world with "Swedish" culture - otherwise it's been almost entirely supplanted by Norwegian culture (and a few Danish provinces in the south).

[TiLT]

Also, one thing that I think is a nice touch is that Scotland is ruled in my game by a Norwegian dynasty (the King was King of Norway and Scotland before I usurped the former title), and so is labeled as "Skottland" in the game.

Neat. "Skottland" is actually the Norwegian name for Scotland. Nice attention to detail there.

[El Guapo]

Also, one thing that I think is a nice touch is that Scotland is ruled in my game by a Norwegian dynasty (the King was King of Norway and Scotland before I usurped the former title), and so is labeled as "Skottland" in the game.

Neat. "Skottland" is actually the Norwegian name for Scotland. Nice attention to detail there.

Yeah, I was pleased when I noticed that the spelling had changed mid-game. I wonder what other country-ruling culture changes are built into the game. I suppose I'll find out, as I plan to take the Danish crown from the current King of Denmark and England (we'll see if it's still "England" afterwards).

[TiLT]

Well, "England" is still "England" in Norwegian, and I don't think it was different back during those times, though I'm far from an expert on the subject. AFAIK, it's only Scotland and Ireland, of the major places at least, that have different names in Norwegian ("Skottland" and "Irland" respectively).

[Isgrimnur]

Austria, France and Germany translate differently.

[El Guapo]

Well, "England" is still "England" in Norwegian, and I don't think it was different back during those times, though I'm far from an expert on the subject. AFAIK, it's only Scotland and Ireland, of the major places at least, that have different names in Norwegian ("Skottland" and "Irland" respectively).

Well right, but I am wondering whether they have different country/name/culture combinations beyond Scotland under a Norwegian dynasty. In the upcoming England example it would be England under a Danish dynasty (so in that case what would matter is England in Danish). What about England under a French dynasty?

Just wondering whether this is an exception or part of something broader. Of course the thing that makes this a bit more rare to happen is that it's not enough for one country to be ruled by a foreign dynasty - it has to be ruled by a foreign King with that as their sole title. Like, before I took the Norway title away Scotland was marked "Norway" because that was the King's primary title.

[El Guapo]

Interesting time for Scandinavia last night. The King of Denmark and England died, and his heir was not yet of age, leading to a regency. Events immediately highlighted how dangerous regencies are, as child (and women) rulers allow for the pressing of weak claims as well as strong ones. And lo, soon after France pressed a claim for the throne of England, and seeing such a fortuitous opportunity I pressed the claim of a courtier (a Prince of Denmark and England) for the throne of Denmark. France's war appears to have failed, but taking advantage of the French conflict I had no issues overcoming a weakened Denmark, and the new King Severin I is now a vassal of the Scandinavian Empire.

A minor snafu is that my previous Emperor wound up having a daliance with a delightful Danish courtier, which produced a son. Since I had no male heirs at the time I took advantage of this and legitimized him. Didn't really pay attention to the fact that the boy was Danish and not Norwegian, and pairing him with a Norwegian tutor failed to change this. So, now I have a culturally Danish Emperor with mostly Norwegian lords. It's been less of a problem than I feared (I get a ~ -8 relations penalty for being a foreigner, but that's bearable - it's the -30 "foreign conquerer" penalty that can be a killer, and I only have that for one or two vassals). But I'll probably still try to get his heir back to being Norwegian.

One other twist is that I was briefly King of Brittany and Aquitane for a couple years. The was a Queen there with no husband and my Emperor married her, giving him those King titles. Though I didn't wind up with control of Brittany (the AI Queen still was in charge). While the Queen and I had a boy he died as a "sickly infant" and sadly the Queen then died before we could have another kid. Ah well, didn't really want to deal with France anyhow.

[Kelric]

I've come back to this in anticipation of eventually buying all the DLC in the next big sale.

Starting out as Munster to get my feet wet again, my second Petty King (who managed to get all three of the southwestern provinces directly under his control so my dynasty now has a very secure power base to take all of Ireland) had to imprison and execute my eldest son as he refused to marry and was somehow part of one of my vassals' courts and refused to join mine. Once my second son married extremely well (not in titles, but in her excellent stats and attributes) and my eldest started a plot to murder my mistress, I had the opportunity to put him away. Because I didn't want him as my heir, I had to bump him off.

Of course, the new heir has only had two daughters so far....

[Kelric]

The heir had a son! And then King Brian Priest-Hater (seriously, that was the nickname he acquired in life) died a few years later, so at least the succession is looking good. Before his death he managed to stake a claim to Ossory, so the Petty Kingdom of Munster is now a full 4 provinces. Of course, the new King can only have a demesne of 3 so he gave Ossory to his bastard half-brother to rule.

Then the Pope called the first Crusade.......

Spoiler:

.... AND NOW I'M THE KING OF THE MOTHERFUCKING HOLY LAND, BITCHES!!

I was so shocked that my little army of 2600 men marched across the European continent, took five holdings from the Egyptian Sultanate and won me enough acclaim to become King of Jerusalem that I saved the game and quit. I don't know what to do next! I have 40+ holdings I need to distribute and the entire religion of Islam to fight off. This is going to get crazy.

[El Guapo]

That's awesome. Honestly no matter what you do you have a time limit on how long you can hold the holy land - basically "until the next Jihad is called." So probably what I would recommend is wait for the levies from the Holy Land to build back up and then use them to help your next European conquest.

[Kelric]

I'm using it to stock my treasury as much as possible right now. It more than doubled my income (all the way to 18.something a month!) so that is a flow that I want to use to build up my Irish capital until I hit my tech ceiling. I got a notification about someone calling for a Jihad but nobody has declared war on me in the year since and no troops have arrived. I'm just going to bank as much as I can in the meantime and try to convert the area to Christianity to cause trouble for their soon-to-be conquerors.

Also, my King is banging his deceased father's third wife (who is younger than he) on the side and has had a son and daughter with her. So his half-sister is half-sister to her niece and nephew....

[Kelric]

Jihad! I lost the Holy Land, but I'm still known as King of Jerusalem. I built up my coffers and will now refocus on becoming King of Ireland.

Edit - Two Kings, a few decades and the Second Crusade later, I'm King of Jerusalem again! I didn't contribute much to the war but as my dynasty somehow still held that title, I got the land. I've absorbed all of Ireland except Dublin (ruled by the Scots) and have half of Wales under my control. I've spent a lot of money over the last two generates, so hopefully I can hold the Holy Land for a decade or so and bump up the treasury once more. Though, I swear, getting so many provinces in one fell swoop almost isn't worth it just because of the hassle of handing out 50 titles in one go.

[El Guapo]

Nice!

Made a nice sizable addition to the Empire of Scandinavia last night, adding all of England (including chunks of Wales and Scotland). The Danish prince that I installed as King of Denmark (under Scandinavian vassalage) also had a weak claim on the English throne. That weak claim only works if the current English ruler is a child or a woman, so... I trade a few assassins with England, and a couple months later there's a new child on the throne of England. Huzzah!

I could field about twice the number of troops that England could, so it was a pretty easy fight. Once the English armies were essentially annihilated it was just a matter of completing a couple sieges to get to 100% war score. Scotland got in late, pressing their own claim on the English throne, so I had to fight a couple battles with them, but that was just a nuisance. And then boom! England's part of the Scandinavian Empire (via being part of Denmark).

What's interesting is just a few months after the conclusion of the war a group of English dukes rebel against the new King of England (and Denmark), seeking to install someone else as King of England (and lower crown authority there). Initially I was going to join the war on behalf of the King of Denmark (seeing as how I'd just fought a war to make him King of England), but then I saw that the leader of the revolt was still my vassal (makes sense since the war made all of England part of my empire). That made me realize that the revolt is probably in my interest, because the downside of the war was that it made my Danish vassal a bit too big - he owns all of Denmark and England, which makes for a problematic revolt if it comes to that.

The rest of my empire can win a war against England + Denmark (I've done it before), but it's still a significant fight and could well be a problem if the King picks the right (wrong) time to rebel. But this revolt would sever the England - Denmark link while keeping all of them part of the empire. So now I'm wondering if I can intervene on behalf of the revolt against my Danish vassal, which would be amusing months after fighting to make the guy King of England.

[Kelric]

30ish years later we still control the Holy Land. I do admit to cheating the last two days though: my current King had two daughters very early in life and two sons very late in life. He has thrice died with his eldest son being only 4/5 years old. I keep reloading, simply because each time it has happened both Scotland and England have declared war on me and mauled me. If it happens again I'm just going to roll with it, though.

[Kelric]

40+ years of the Holy Land under control and converted to Christianity, and fourth time the charm on keeping my King alive until the Heir reached maturity. My King is still only in his early 60s, so he was never particularly old, he just kept dying. He wouldn't even get sick or wounded, he would just keel over. Luckily he lived this time since I was able to assassinate the heir to the English throne, and the English don't let women inherit at all, so King Torf the Great will now see his throne pass to a cadet branch of the English dynasty. That branch has a 50-something year old heir with no children, and his only brother is 30-something with no wife and is a celibate Priest. I am in the middle of helping Torf put down a rebellion by a very populous Godwin (Godwinson?) line, just married my heir to Torf's 3rd daughter, and am cultivating a relationship with Scotland to see if I can eventually move to have my King's grandson fight for England.....

Crown authority is at maximum, vassal levies are at minimum, and my demesne ranking lets me carry 8 castles. I only have 7 at the moment in anticipation of my King dying and the Heir not being quite as awesome, but even if I need to drop one I can drop Jerusalem when necessary and keep my Irish/Welsh power base.

This past day or two of trying to keep my King alive is the only time I've reloaded a prior save in this game, so up until then this may be the best I've ever done by the year 1200 (in 1198 or so right now).

[TiLT]

One nifty thing about saving in this game is that achievements are completely disabled as long as you don't play on Ironman mode. If you want to earn achievements, then you'll have to accept not being able to abuse the save/load mechanic.

[Kelric]

So then my King died and all my vassals hated me. After about a thousand gold worth of bribes to make them hate me slightly less, I had half a dozen plots still raging against me..... then two Jihads were called at the same time! TWO!

Spoiler:

STILL KING OF THE MOTHERLOVIN' HOLY LAND, BITCHES!!!

Called up my English father-in-law and two of the three Holy Orders (and married the King's heir/younger brother to another English princess) , then proceeded to rampage throughout the Holy Land on the defense and slaughtered Muslims left, right, up, down, center, rear, diagonal and everything in every other direction! Took six years, but we got a White Peace with everyone and now my vassals and most of Christendom love me.

Edit - And then Scotland & Norway team up to take Ulster from me and I win that! Fuck yeah! (Barely, with two mercenary troops coming on board and depleting the treasury.)

So a decade of war, 1,000 gold less in my treasury, and my subjects love me but I have no more land.

[El Guapo]

Nice! I recently (as Emperor of Scandinavia) went and won my first crusade, only I didn't know the "outstanding King of Jerusalem" rule, so the holy land was returned to the previous holder of the title (Queen Mor of Brittany). Which was annoying, but I did get a fair amount of prestige and holiness for it (plus the "Crusader" trait is nice). Plus I previously married my uncle to Queen Mor, so the King of Jerusalem is a member of my dynasty (the Al Freyseys), just not me. Actually it seems like it's always a good idea to join a crusade, even if you can't really contribute significantly - just getting off the boat in the Holy Land gets you the nice Crusader trait.

Otherwise I added the King of Wales to my titles - pretty easy since Wales was scattered, so I could use my English forces to steam roll them pretty easily. Probably going to give that title to my youngest son. Also I married my heir to the Queen of Pomerania, so when his eventual heir rises to the throne he should add Pomerania to the realm.

Also interesting is that probably 100 years ago the Mongols showed up - Golden Horde and Ilkhanate. Interesingly they seem to have christianized and integrated into the European power structure. I notice that Poland, for example, is now the "Khanate of Poland" - ruled by a nice pecheneg catholic fellow (presumably installed on the throne by one of the tribes). Doesn't really seem to have changed much.

[TiLT]

I quickly learned that going on crusades is worth it, even if you lose. If the opposition is too strong for victory to even be possible (which can happen all the time if you're facing a united Arabia), all you have to do is sail into the Mediterranean and look for isolated troops to hit & run. If enemy troops become too threatening, withdraw by boat or simply disband your army to have them return home through their own means. There's no need to put your ruler at unnecessary risk. You merely want to participate in a few small battles and give your ruler the Crusader trait. Governing becomes so much easier afterwards, as everyone will gain new-found respect for you.

[Cortilian]

Couple of questions.

1. I started as Munster and have united Ireland under my control. I now want to set my sights on Scotland. How do I gain Casus Belli against the king of Scotland? And how do I take over Scotland. Can I just take his capitol or do I have to take every county?

2. I've never participated in the crusades. How do I do that? When the crusade is called do I just load up my troops and head to Jerusalem or do I need to talk to the pope or something?

[TiLT]

1. I started as Munster and have united Ireland under my control. I now want to set my sights on Scotland. How do I gain Casus Belli against the king of Scotland? And how do I take over Scotland. Can I just take his capitol or do I have to take every county?

Essentially, you can't just set your sights on another country and decide that you want to take them over. There are certain requirements, and they are strict. Here are a couple of options:

1) If the other kingdom contains more holdings than your own, you can use the Invasion CB. I believe this requires asking the Pope for permission, which also means that he needs to like you and/or dislike the other ruler.
2) If the other ruler is a heretic or of another religion, you can have a crusade declared upon him, once again by the Pope.
3) You can inherit the country by marrying into the other ruler's family in such a way that the marriage will produce one of your future heirs. This will give your heir a claim on the kingdom.
4) You can take the kingdom piece by piece. You do this by pressing claims against smaller parts of it, preferably duchies. Use fake claims for this. Keep in mind that such wars will create a truce with the other ruler afterwards. You can get around this by pressing claims on rebel factions whenever they appear. Once you have more than 50% of the kingdom's de jure counties, you can usurp the kingdom title.

As you can probably tell, taking over another kingdom is a massive undertaking in most circumstances, and it could take several generations to pull off. Plan ahead.

Wars to take over kingdoms are no different from smaller wars, except in their scale. It's all about pushing your war rating up through any means necessary. This includes killing enemy troops, occupying holdings, and so on. Taking the capital isn't necessary, but it provides a large boost to your war score.