The Steppe Menace
In almost every game of Crusader Kings II, there will come a time when an army of vicious pillagers known as the Mongols will come to seek conquest and riches in the West. As a ruler or vassal of the West, it is your duty to protect the realm from this seemingly neverending horde of Steppe Wolves. There are many obstacles for the Mongols, but in this page, you will understand that no obstacle is too large for the Horde. And as an end to this introduction, I will quote the words of Captain Kirk, Star Trek Wrath of Khan "KHAN!!!!!!".
If you start from the very beggining at Stamford Bridge, you will get almost 155 years to prepare for the atrocities that will soon arrive from the East. At around 1216 - 1240 (In my experiences), you will recieve a message detailing the rumours of a Mongolian Khan uniting all the tribes and are heading your way, if you studied your history you will know that these rumours are unfortunately true. A few months later, you will recieve a second message, the Scourge has arrived!!
In your first playthrough, you will immediately look to the east, you'll ask, "I don't see a Mongol realm, where are they?" The Mongols don't start with provinces, they are known as the Illkhanate, they will attack one of the realms at the Southeastern edge of the map, most likely the Seljuks or Khiva. You're going to ask another question, "They have no provinces, how do they win?" Simple, the game gives them 4 - 6 doomstacks of up to 20k soldiers to loot and pillage as they please. The next thing you need to know is that these armies are attrition proof, no soldiers will be lost unless in combat, that means you could see a 100k doomstack without a skull near the numbers. The Mongols attack nations with a Casus Belli that they have on every realm that is not Mongol, it is basically a subjugation CB, as in most games, I find that the lords that don't die in battle retain a few meagre titles and serve the Mongol opressors, but they eventually get replaced by Mongols, did I mention the Mongols get Unlimited Demense? As Basilieus of the Byzantines, you don't have to worry as much, the Illkhanate usually never reach the Mediterranean and because of their huge threat to the Muslims, you'll find a lot less or at least laughibly weak Jihads comming your way. And as a Catholic Ruler, you can just sit back and laugh your ass off as the Mongols tear apart the Muslims who are probably in civil war, Jerusalem will be much easier to take while the Muslims are busy fighting the Mongols.
Dealing with the Scourge
To deal with the scourge, you should wall off all acesses to your base with bunkers and fill them with marines and firebats, wait, that's the wrong game, sorry. As a Catholic, you can just sit back and laugh as the Muslims get torn apart, get your armies ready, Jerusalem is ripe for the taking!! As a Orthodox, you should be cautious, watch their expansion carefully, if they reach your borders which they most likely won't you could potentially be next in their quest to gobble up the map. Try to keep your realm united and strong, vassals fighting eachother and decreasing the number of vauluable levies ready to be raised incase the Horde starts looking at you more viciously than usual. As a Muslim (Can be played through mods or the Sword of Islam DLC) that rules in the Middle East, you are the most immediate in danger, keep your armies strong and your vassals friendly, the last thing you need is for some idiot who thinks taking 2k from your already outnumbered army is a good idea. You always need to outnumber the Mongols to win, you might get lucky in some cases, but Horse Archer spam will put your troops in the shade, a shade created by a cloud of arrows coming right down on your ruler ending his rule and causing a succession crisis. The Mongols will most likely assault every city they reach, let them lower their numbers and morale abit before attempting an attack, a 20k horde with full morale can devistate your horde of 21k that's going to lose 3k troops in 2 days, while your attack comes in 3 days. That's basically the only tips I can give you about combat, now you got an idea, "I can assassinate their rulers one by one, creating a succession crisis and a civil war that tears apart the horde!! I'm so smart!!" No you're not, but I don't blame you, one, that is really expensive. Two, you're wine is going to taste funny if you fail. Three and MOST importantly three, every Mongol Khagan gets a special event to call in reinforcements, they can only do this once in their life, so killing one Khagan doesn't bring just a new Khagan, but an army of 40 - 80k ready to play with the rest of the horde. That's right, every ruler gets a one time use which they will most likely use that brings in more Mongol buddies, leave the Khan alone, or pick your poison, funny tasting wine, or 160,000 Mongols knocking on your castle door.
Victory!!? Oh snap!!!
So the Illkhanate's push is slowing down and you notice some provinces are occupied by rebels and Muslims, you think you've won? Even though you probably did nothing. (Unless you were a Muslim ruler). Well guess again, Genghis back in Mongolia, decides he needs another Horde, so he orders more men into the small pixelated world of Crusader Kings II. Now you're thinking, "Haha, those Muslims never get a break do they?" Well think again Mr.Catholic or Orthodox ruler, this Horde is going to appear in the Northeast, and they are known as the Golden Horde. So now you've rethought things, "Okay, but the Pagans and Cumans are going to hold them back." Wrong, if the Muslims couldn't hold of the Illkhanate, then the Golden Horde is going to easily take the underdeveloped provinces of the Heathen Pagans. These Mongols are not going for the Mediterranean, they're going for a different ocean, the Atlantic Ocean. The French don't have to worry though, nothing's gonna get past the Holy Roman Empire, so they can just go back to inheriting land from the English and Germans or Holy war their way through Iberia. As a Orthodox Ruler, you are now in the Muslim's shoes, an invincible Horde has appeared and is marching to your border, get your armies ready for the declaration of war, build up defences and prioritize military over domestics. The tactics for the Golden Horde are the same, they are pretty much the exact same thing as the Illkhanate but they operate in a different area, which is easily swiped away creating the Mega Blob of Golden Horde. The tips are the same, leave the Khan alone, attack where they are weak and flee where they are strong, fight where you want to fight and not where they catch you.
Okay Victo- Oh come on!!!!
Okay so both the Illkhanate and Golden Horde have stalled and are suffering from internal struggles and holy wars from the Orthodox and Catholics to claim land. So now you're wiping off the sweat with your towel, but when 1290 - 1310 roll by, you're going to squeeze that towel in complete shock after the message you recieve, then you cry now that there is sweat all over your keyboard. The message speaks of a new threat, some jerk named Timur wants to beat Genghis' record as largest contigous Empire in the world. Timur is going to arrive somewhere around the Illkhanate area, if they still exist, Timur is going to take them first. Since you're further into the game, your tech is pretty strong and your demense provides 10k troops every province, you're going to have a easier time, but nevertheless, they are practically the same Horde you know and love. The tips are pretty much identical to the Illkhanate, so stay strong and they'll go away eventually.
Things you need to remember and know:
-Every Khagan that succeeds can call in reinforcements of 40 - 80k troops, let them live long lives or they are going to outnumber you pretty quickly.
-The Illkhanate arrive around 1215 - 1240
-The Golden Horde arrive around 1230 - 1255, just shortly after the Illkhanate
-The Timurids arrive around 1290 - 1310
-The Hordes are attrition proof, the levies they raise aren't, the only thing going to subtract from their troop numbers is Steel and lots of it
-Horde troops require no upkeep (probably from all the looting they do, it's a historical thing they don't sack the cities back to the stone age in CKII)
-The farthest the AI Mongols have ever expanded for me was the Illkhanate fighting for Jeruslam, but somehow ignoring the Byzantines, and the Golden Horde were invading Sweden, the Timurids usually never make it far though
-The Hordes are not invincible!! Keep at it!! They will eventually be pushed back, even if that means you get owned before it
-The reinforcement event can be void if the Horde is converted to another religion or the year is past 1300, so either change the Horde's religion or hold out until 1300, then you can assassinate them as you please!!