中国（英文：China）是 
碧玉之龙DLC引入的地图外势力。尽管中国皇帝个人不拥有土地，他的都护在大多数开局都拥有领地，并在CKII的世界中充当他的利剑。中国皇帝和西域都护府永远存在，即使都护府失去所有领地。所有在中国外交范围内的领主都可以和中国互动，可能使他们获得强大加成和可怕制裁。知道如何巧妙地利用中国机制是在地图东侧获取权利的关键，既要消灭敌人，又要确保皇帝永远不会让军队转攻自己的领地。
一般事项
中国，虽然是地图外势力，但仍可能发展并交替出现数不尽的势力和极度痛苦的阶段。统治者可以选择是否利用之；但他必须注意，在没有能力打败中国时，不要激怒巨龙。
国情
国情 表示中国的状态, 是对天朝太平或动乱的描述。它影响着天朝国策方针和邻国通过丝绸之路获得的商业利益。国情以完全随机的方式发生改变，一种国情'极少'持续超过十年， 但是， ‘’ 政通人和 ’ ’ 持续的比其他国情都要长, 并且 " 太平盛世" 一般可以持续超过五十年!(我华夏，天下无敌啊！)
| 国情 | 描述 | 效果 |
|---|---|---|
| 政通人和 | 中国正处于内部安定时期，且与东方的贸易颇有利益。因为没有大规模灾难或是强大的敌人，繁荣得以传播，而中国的军事力量也准备好保卫其财富以及它忠诚的朝贡国们。 |
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| 国局动荡 | 一场动乱在中国国内蔓延。它已经把丝绸之路的东段破坏了。为了维持秩序，中国军队已经全部被调回本土，除非动乱平息，不然一场全面内战随时可能爆发。 |
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| 内战爆发 | 中国爆发了一场内乱，导致东方贸易受挫。帝国的军队陷入内讧，统治的王朝也受到威胁。强大的将军或许会越过中国边界，前往西方寻求财富。 |
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| 蒙古压境 | 北方的蒙古部族侵入了中国，强大的中国军队正殊死防御着帝国，这场战争极大地扰乱了贸易秩序，同时导致了大量的难民流离失所。当战况恶劣时，正统王朝的后裔可能向西流亡。. |
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| 女真南侵 | 一个拥有大量女真骑兵的巨大部族正从冰冷无情的东北南下中原。强大的中国军队正专注于防卫其这孤注一掷的猛烈入侵。这场战争破坏了沿丝绸之路的贸易，并可能造成了大量难民外逃。如果女真人胜利，那么当朝皇族后裔有可能与他们残存的军力向西流亡。 |
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| 饿殍遍地 | 严重的歉收导致粮食不能满足人口需求。这场灾难导致大多数贸易停止，当发生人口减少的饥荒时，曾经强大的军队肩负起赈灾的工作。 |
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| 瘟疫横行 | 一场可怕的大瘟疫在中国爆发了，它首次出现就带走了成千上万的人命。中国的经济已经陷入崩溃，贸易也停滞了，甚至就连帝国的军队也遭受了毁灭性的打击，无力对抗全盛时期的敌人了。 |
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| 黄金盛世 | 中国已经得到了无穷无尽的力量和财富。随着中国的繁荣昌盛，东方的贸易路线不止带来了前所未闻的珍贵商品，还带来了富有和充裕的华夏文明的例证。 |
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中国仅在政通人和或黄金盛世时期可以被征服（通过“入侵中国”选项）。参见本页的“采取敌对行动”和“入侵中国”了解细节。
政策
政策是描述中原王朝当前对外政策的特性。当皇帝驾崩新皇登基时，可能改变政策，但新皇帝很可能延续先皇的政策。困难时期，皇帝很有可能选择门户开放，而处于黄金盛世的皇帝可能成为扩张主义者。任何中国国情都可能选择闭关锁国，即使其被选择的概率很低。
| 政策 | 效果 |
|---|---|
| 门户开放 |
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| 闭关锁国 |
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| 开疆扩土 |
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皇恩互动
所有和中国的互动都基于游戏中一个新的交换值，称作皇恩。皇恩代表中国欠一位统治者的恩惠，可以通过不同方式获得或失去。统治者拥有的皇恩只和一个中国统治王朝有效。如果一位篡位者或侵略者夺取了龙椅，所有的统治者都会失去他们的皇恩，不得不重新开始建立良好的关系。
获得皇恩的方式有两种：一种是按时送礼或进贡角色侍奉皇帝，另一种是向皇帝表示臣服，这将使统治者及其后代每月稳定地获得皇恩。
同时注意皇帝的喜恶显著影响皇恩的获得。通过以下方式：
- 和皇帝同文化将给予统治者每月1.0皇恩。
- 如果他们信仰相同的宗教，同上
- 拥有皇帝喜爱的文化/宗教给予你每月2.0皇恩（进入中国界面来查看你是否满足条件）
通过互动获得皇恩
为了获得皇恩，统治者有一系列的决议，这将要求他放弃游戏中的特定元素（例如，一位廷臣，一位家族成员，钱，宝物……）。领主牺牲的越多，获得的皇恩回报越多。注意每个决议或行动每25年只能采取一次。在玩家当前统治者去世后决议的计时重置，允许玩家再次采取该决议。获得皇恩的决议有：
| 决议 | 描述 | 条件 | 获得皇恩 | 修正 | 结果 |
|---|---|---|---|---|---|
| 进贡宝物 | 奉上一件无价的宝物给中国皇帝。他一定会高兴的。 | 任何宝物：
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品质3获得250，品质4获得5000，品质5获得10000 | 如果皇帝喜爱你则+50%，如果他讨厌你则-25% | 此宝物消失于皇帝之手 |
| 赠送礼物 | 向皇帝赠送一大笔钱 | 在你的国库有四倍年收入的钱 | 300 | 如果皇帝喜爱钱则+100%，如果皇帝喜爱你则+50%，如果皇帝讨厌你则 | 这笔钱先给都护，再给皇帝 |
| 进贡侍妾/面首 | 向皇帝进贡侍妾/面首，充盈他的后宫 | 任何廷臣：
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取决于：
所有修正可叠加。 |
如果皇帝喜爱你进贡之人则+100%，如果他喜爱你则+50%，如果他讨厌你则-25%，如果他讨厌你进贡之人则-50% | 被选中的廷臣将永远离开你的宫廷去中国 |
| 进贡宦官 | 将你的一位廷臣送去中国做宦官 | 任何廷臣：
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取决于：
所有修正可叠加。 |
如果皇帝喜爱你进贡之人则+100%，如果他喜爱你则+50%，如果他讨厌你则-25%，如果他讨厌你进贡之人则-50% | 被选中的廷臣将永远离开你的宫廷去中国 |
| 进贡指挥官 | 向皇帝进贡一位指挥官 | 中国必须处于国局动荡，内战爆发，或者面临女真或蒙古的入侵
任何廷臣：
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取决于：
所有修正可叠加。 |
如果皇帝喜爱你进贡之人则+100%，如果他喜爱你则+50%，如果他讨厌你则-25%，如果他讨厌你进贡之人则-50% | 被选中的廷臣将永远离开你的宫廷去中国 |
| 成为朝贡国 | 在艰难时期，成为中国皇帝的朝贡国可能是必要的 | *独立统治者
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+ 2 每月 | 无 | 会成为中国的朝贡国，把你50%的收入，30%的军队补员速度给都护，同时还有在战争中加入他的义务，并且每月声望-4.0 |
| 进贡马匹 | 虽然没有标志着完全屈服，赠送马匹有利于让中国高兴 | *游牧统治者
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+ 2 每月 | 无 | 获得一个修正使你的  -15%补员速度
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| 在皇帝面前磕头 | 到中国去表明你承认皇帝的统治可能是一种耻辱，但这反过来会保证他对你的支持，并且给你一个发现世界的机会 | *统治者
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取决于事件链中的选择，威望和级别。角色将获得一个特质，给予+1, +2, +4 每月皇恩（同时 -0.1 每月威望） | 无 | 旅途中，统治者将-0.5健康，并接收许多事件(详细信息在下文)。最后，取决于角色的级别（越高，他会越丢脸），损失100/250/500/1000的声望 |
| 派遣救援队 | 当中国面临巨大的困难时，送去一些军队和资源来减轻人民的痛苦，肯定会使皇帝心怀感激 | *处于和平
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500 | 无 | 将获得修正向中国送去救援物资，国家税收修正-10%，征召兵补员速率-30%，持续10年 |
| 派遣医生 | 当中国正遭受瘟疫的蹂躏时，派遣一名医生可能有助于皇帝控制疾病造成的损害 | 任何廷臣：
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取决于：
所有修正叠加 |
如果皇帝喜爱你进贡之人则+100%，如果他喜爱你则+50%，如果他讨厌你则-25%，如果他讨厌你进贡之人则-50% | 被选中的廷臣将永远离开你的宫廷去中国 |
军事属性大于等于12
学识属性低于8则-50，8-11则+40，12-15则+60，16-19则+100，20-23则+140，24-27则+180，28-31则+220，32及更高则+260。花费你的皇恩
一旦统治者获得足够多的皇恩，他可以使用它来采取一系列与皇帝有关的决议。虽然获取皇恩的条件严格，但使用皇恩没有条件。一位统治者每年可以向中国求取一次帮助。决议有：
| 决议 | 描述 | 条件 | 所需皇恩 | 结果 |
|---|---|---|---|---|
| 请求和平 | Ask for a peace treaty with the Emperor, to ensure he will not attack you in near future | *Has more than 250 Grace
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250 | The Chinese Emperor guarantees that his General Protector will not engage you with tributary wars or great invasions in the next 50 years. On the other hand, you will not be able to pillage China in the meantime. |
| 请赐天朝医师 | China has very effective ancestral practices. Recruiting one of its talented physicians could help coping with illness | *Has not already a Court Physician
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250 | A Chinese physician with the trait  enters your court
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| 请赐中国宝物 | China has many wonders to offer. Perhaps the Emperor could spare one to you | *Not pillaging or invading China
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500 | A random artifact from China of quality 1 to 3 is given to you by the General Protector |
| 请赐攻城专家 | Over time, China has mastered siegecraft. You can ask for some of them to join your court for your own needs | *Not pillaging or invading China
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750 | Three Chinese siege engineers with  (+50% siege speed) join your court
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| 请赐兵法家 | Chinese generals have become masters in warfare. Having one at your service might serve you well | *Not pillaging or invading China
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750 | A  from China joins your court. Once in a while, he will teach your commanders one Chinese leadership trait ( ,  ,  ,  )
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| 请赐士大夫 | China has produced very efficient administrators. Having one at your service will greatly enhance your demesne | *Not pillaging or invading China
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1000 | An erudite will join your court. As long as he will stay alive, you will have a modifier granting -15% construction cost and length |
| 请赐将作大匠 | The Chinese Empire is home to many technological inventions. Hiring one of its engineer will make you leap forward technologically | *Not pillaging or invading China
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1000 | A master engineer joins your court. Once in a while, he will grant your demesne counties a bonus of technology spread rate, tax income, or levy/navy size and morale. He will build such building every 2920+/-1095 days (if Golden Age in China 1460+/-542 days). He will privilege county where there isn't a modifier and your capital first before a non-capital county with already a modifier. |
| 请求与皇室联姻 | The Chinese Emperor is a powerful protector. Securing a marriage with one of its family members would guarantee his protection | *Not pillaging or invading China
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1000 (750 if already have a peace deal with China) | An Imperial Prince or princess will marry the family member. You will gain 500 Prestige, a peace treaty with China. Whoever court he belongs to will be able to raise one imperial regiment when at war (With 500/1000/1500/2000 event troops according to the rank, disbanded after the war) |
| 请求互市商约 | The Silk Road starts in China. As such, a commercial contract with Chinamay attract its favours, and its merchants | *Not pillaging or invading China
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2000 | A commercial contract is signed. For 25 years, all Silk Road trade posts in your realm will get +100% revenue. |
| 请求入侵 | China is renowned for its mighty armies. Maybe the Emperor could help you to destroy a powerful rival... | *Not pillaging or invading China
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5000 | The General Protector declares war on your target. If he is victorious, all realm and empire rank titles held by the target will be destroyed, leading to the dismantlement of its realm. |
Taking hostile actions
Any lord bordering the eastern edge of the map may take hostile actions against China. The options can be viewed by clicking on the sword icon below the portrait of the General Protector. There are three actions possible: pillaging, forcing to open and invading China. Only the invasion requires an armed conflict and leads automatically to war, whereas war can be avoided with the two others. Nonetheless, one should consider with extreme carefulness his options when making the choice to attack China, as the consequences of a failure can be very dire.
Pillaging China
The common hostile action taken against China is to pillage it. This can be started only once every 5 years, as after stopping it the lord involved in pillaging will receive a modifier, Recently pillaged China, disqualifying him for any action with China, be it regular interactions or hostile actions, for the 5 years to come. Once a lord elects to start pillaging China, he will receive a negative modifier, Pillaging China, giving -10% levy size, -15% levy reinforcement rate, -15% manpower reinforcement rate, -25% commercial revenue and -10 monthly Grace. In addition, interaction with China will be impossible for as long either of the modifiers is active. On the other hand, every year, the pillaging will receive a booty equivalent to 3 months of income (minimum 15, maximum 75 gold), along with 50 Prestige. On the flip side, if China’s policy is Expansionist, the ruler will be a priority target for a Chinese Invasion
Several events can occur while a lord pillages China:
- Upon pillaging a border city, the pillaging soldiers may encounter an apprentice of a great Chinese siege master. They will bring him back to the lord, which will gain for free a general with , along with 75 Prestige and 125 gold.
- While burning down the house of a great Chinese noble, the troop might kidnap one of his children, typically one of his daughters. The unfortunate maiden will be brought back to the pillagers' court, where her excellent education and traits such as
or 
will make of her a prized wife and courtier. - While pillaging a village, the marauders may encounter an artifact. Their lord will gain 75 Prestige, and 100 gold, along with a random Chinese artifact.
- While raiding trade caravans, one's soldiers may encounter a precious silk and porcelain loot. The lord will earn 150 Prestige and 200 gold
- On their way to another village, the pillagers may encounter a Chinese patrol. Unable to defend themselves, they will be massacred and their lord will lose 50 Prestige
‘’Note: Even without electing directly to pillage China through the Interactions screen, a ruler whose troops are set to Pillaging which sends them to a territory directly owned by the Western Protectorate will still have the -10 ‘’At War’' Monthly Grace modifier for as long as he will be considered Hostile by the General Protector (180 days + all the time the ruler’s troops spent pillaging his territory). This modifier does not stack up, allowing to both pillage the Protectorate and the Empire without further Grace maluses
Force China to Open
This action can be taken while China adopts the Isolationist policy, effectively ending all trade revenue for the Silk Road. One angered and powerful lord may try to end this, by negotiating with China or threatening China with military retaliation if it doesn't open up. If China is left unimpressed, it will result in a war. If the lord wins the war, or if China accepts to re-open via negotiation (usually demanding the lord to become a Chinese tributary, sending back one of his Chinese subjects, or destroying one of his trade posts in exchange), the policy will switch to Open, and Trade will resume in the Silk Road.
Also, if a single lord's realm (the player, mostly) controls over 25% of the trade on the silk road and controls a starting point of the silk road, the lord has the choice to directly force open China (by luring merchants out of the border) without needing to negotiate or fight wars with China. China will be displeased with this act and the lord will lose 1000 grace with China as a result. If China is force-opened this way during Golden Age, there is a 30% chance that the status of China immediately changes from Golden Age to Stable as a result.
Invading China
As the ultimate proof of his power and glory, a lord (with the rank of emperor) can try to invade the whole Chinese Empire in order to place a Dynasty member on the Dragon Throne. If he wins, he will gain 10000 Gold, prestige from war contribution (up to 5000 prestige if 100% war score), 5000 Grace, +10 Monthly Grace due to being of the same dynasty as the ruling Emperor, (potentially +1.0 if same culture and another +1.0 if same religion), be favored on the Silk Road for 50 years (all Silk Road trade posts in the realm will get +100% revenue), along with four great quality, level 4-5, Chinese artifacts (Jade Dragon, Dragon Amulet, Jian, Water Clock). He will also receive all the land and vassals the Western Protectorate owned, along with a 50 year Peace Treaty with the new dynasty of China. The new emperor will travel to China with all his immediate relatives (spouse, children, siblings) that are landless and not heirs to any titles. On the other hand, if the invasion fails, all Kingdom and Empire titles the lord owned are destroyed, thus releasing all of his Duke and above-ranked vassals and dismantling his country. He will also lose 3000 Prestige, three years of income as war reparations, and gain a -2 Monthly Grace and -0.1 monthly prestige modifier, "Angered the Dragon", for 50 years, making him a prioritized target for the Western Protectorate. The lord will also not be able to interact with China in the future. Moreover, the war to invade China is not possible to reach white peace, so the lord could only either win or lose the invasion.
Needless to say, taking this decision can have very dire consequences. Successfully placing a dynasty upon the Dragon Throne is not a Steam achievement, due to the supreme difficulty of the adventure. As such, it requires very careful preparations, and well-rounded strategies in order to warrant success in this invasion. (For more detailed insights about how to make any starting state a world-class military power, see The Art Of War).
First, one should pay close attention to the current Status and Policy of the Chinese Empire. China can only be invaded during Stable or Golden Age status. Successfully invading a Stable China would require a well-developed mid to late game empire with large army and gold reserves, as the Protector General will immediately receive at most 172.5k (172250, to be precise) attrition-free Chinese event troops led by generals with Chinese leadership traits to defend the Empire. In addition to the initial event troops, China will also periodically send in reinforcements (maximum 50k event troops each time) if the war stays indecisive. Attacking China during its Golden Age will make you face Chinese event troops with significantly higher combat ability and even better generals.
Note that the number of event troops China spawns is normally scaled to the number of the attacker's army in order to outnumber the player's troops, and Golden Age China has a higher multiplier than Stable China in the calculation of event troops spawned. Yet, there is always a cap value of ~172.5k (172250 event troops) for the Chinese event troops spawned, meaning that the Protector General can receive at most 172.5k event troops both in Stable and Golden Age status, and the policy of China (Isolationist, Open, or Expansionist) does not affect this cap.
Thus, the Chinese Empire in its Golden Age is a properly enormous power (as to compare, Seljuk spawns with 60k event troops max, Genghis Khan with 100k, and the Aztec with their second wave reinforcements can at the very most have around 185k fairly weak event troops with low combat abilities). In addition, China will send its most talented commanders to face your armies, making the effective strength of the Chinese armies in average 30% stronger than the rough numbers.
Your own numbers should match the ones of the Chinese if you want a comfortable chance of winning, but having high Technology in key domains (Cavalry, Heavy Infantry, Military Organization for reinforcement limits) is equally important. You should also have the most talented commanders you’ll be able to find, maybe even Chinese ones in order to match the power of the Chinese armies, with preferably at least one 
or one as to escape unwanted battles.
The invasion of China should be a well planned attack. As defeat must be avoided at all cost, a large-scale rehearsal could be a regular war with the Western Protectorate. When feeling confident of your strength, declaring war on the Protectorate with regular CBs could let you assess your real chances and proof your strategy in the best conditions (though China will usually send an even higher number of event troops in a real invasion). The only consequence of defeat will be a one-time payment that will sink your treasury for one or two years at the most.
The terrain must also be mastered, as the Chinese troops will either spawn in the county of Samatata in de jure Kingdom of Bengal with equivalent amount of ships or in the county of Jiuquan in Hexi-Gansu Corridor (Both are on the eastern border of the map), depending on where your realm borders China or the Western Protectorate. Ideally, you should secure a proper area of supply in one of these two regions, since unlike the Chinese event troops, your troops won’t, for the most part, be event troops that escape all laws of reinforcement, be it attrition or reinforcement rates. You will have, in order to be able to gather enough troops to win your battles against the Chinese doomstacks, to maximize the supply capacity of your counties to make the fight the least unequal possible.
Once all the preparations and rehearsals made, the invasion can be initiated. Due to the high quantity of the Chinese troops, and their invulnerability to attrition, your main concern should be to avoid facing all of them at one time. Although the initial stack is systematically divided in sub-units of 20k-40k troops, the sub-units normally still have significant movement speed bonuses, and can band together and quickly support each other in battles.
Your first goal should be to break the initial momentum of this great quantity of Chinese troops. Gradually pull back your stacks (pay close attention to attrition), then after the initial stack has divided into sub-units of 25k troops and headed off into different directions, start conducting small skirmishes involving 1 or 2 sub-units at a time in order to start diminishing their numbers and disorganize the wave that comes to flood your lands. All the while, your troops should be left in several armies fitting the reinforcement capacity of their regions, with 1-2 counties of the Chinese armies.
While skirmishing in such way, your troops should then be concentrated in order to gain local superiority against the weakened Chinese units. This will be the time of the great battles, with several dozens of thousands of troops on each side, and equivalent numbers for the dead. It is the critical phase of your invasion, as you will need to win most of the skirmishes to cripple the Chinese advance, and to bring their enormous numbers to more decent levels.
Finally, once the event troops don’t post immediate threats, or while battles are fought, some of your troops should be spared and sent to besiege the Protectorate’s territory (especially the capital province) and retake lost counties in order to earn the occupation warscore required to finalize your invasion.
While following these steps isn’t necessary, it can help coping with the most dangerous aspect of the invasion, namely the initial wave you’ll have to face. As the Chinese will lead sub-units of 20-40k soldiers with very competent commanders, taking over your counties will be very easy for them and it will initially cost you a significant amount of warscore. Yet remember, in "Invasion of China" war, the maximum amount of warscore that the player can lose from occupied (or gain from occupying) counties is locked to -50%/50%, so occupied counties would not force the player to surrender. As long as you picked the right fights by picking off 20k-40k mini-stacks, sieged down Protectorate General's counties whenever possible (especially the capital, as occupying the capital and a significant number of other counties directly-owned by the Protector General gives you a chance that the Protector General will surrender to you without reaching 100% warscore), skillfully arranged your regiments to avoid grim attrition, you will have a good chance to win against China and seize the dragon throne for your dynasty!
As signing a white peace is impossible during the invasion, there can only be two possible outcomes. While the risk to undertake is enormous, successfully invading China is the crown jewel of any CK2 campaign, and a very exciting challenge to face.
China at War
Although absent from the map at most start dates, China doesn’t just sit in its corner. The Western Protectorate can be very often at war, and slowly expand the Chinese dominions from the Jiuquan province up to mainland India, or even all the way to Biarmia. Due to the large amounts of troops it disposes of, China presents a very tangible threat to most nomadic Khanates but also to divided states in the Tarim Basin and the Tibetan region.
Tributary Wars
Most often, the Protector General will attack a state in order to make him an Imperial Tributary. An Imperial Tributary will lose 50% of revenue, 30% of Troop reinforcement rate to the Protector General, along with an obligation to join him at war and -4.0 Monthly Prestige. He will gain, as a compensation, the ability to levy an Imperial battalion for his defensive wars (similar to the one gained through Imperial Marriage).
This war follows the usual mechanics, and the Protector General will receive event troops scaled to the troop count of the primary defender to assist in his war, and call for the support of his Tributaries. Defeat is highly unlikely for the Protector General, as he attacks very often small states with few troops. Sometimes though, this war can still be won by the defender thanks to ticking warscore, as the General’s AI can sometimes forget to unleash its troops after an initial trampling, leaving enough time to the defender to recapture all of his territories.
Another although rarer war with the tributaries can occur when a Tributary feels confident and powerful enough to break free from the Chinese yoke. Just like in a war led by an Independence faction, the attacker benefits from the ticking warscore. Careful skirmishing and quick sieges can thus ensure a victorious campaign even without numerical superiority.
Even if relative power is the main criteria for the Protector General to attack a state, other factors play a significant role. A lord pillaging China is more likely to be attacked, whereas a nomad sending horses has fewer chances to be subjugated.
Great Invasions
Sometimes, the General Protector can engage in more ambitious campaigns, making him a real threat to all rulers on the Eastern side of the map. These Great Invasions can be decided only if China’s policy is Expansionist, and if Great Chinese Invasions are enabled in the game rules. Once declared, the General Protector will attack any state bordering the East of the map or his territory, summoning along with him the double of the amount of troops he normally has (as China is set on Expansionist) and his Tributaries.
This time, the outcome of the war can be far more uncertain. As it is an Invasion, the defender is very unlikely to surrender anytime before -100% warscore, differing in this way with Tributary Wars that often conclude with a pacific submission. His chances depend directly of the amount of troops he has, as great battles are unavoidable this time, and the support of the neighbouring states, which can join his war. Invasions are often bloody for both sides, and lead to longer wars than the Tributary ones.
A Great Invasion, once concluded, can either lead to the victory of the Defender (which will gain significant Prestige and wealth), or the one of the attacker. In this case, all properties occupied are usurped, and the General Protector subjugates the defender. If he is king or below, he will only be vassalised, but if he is an Emperor all his Emperor-rank titles are destroyed before he is vassalised.
Losing a Great Invasion is a terrible fate for a ruler. He will become a subject to the Western Protectorate, forcing him to form powerful enough factions to break free. In the Confucian Bureaucracy, all religious or cultural opinion maluses with the liege are negated, making it difficult to form a cluster of rebellious vassals. The only hope for the defeated is to wait for China to become unstable, before declaring war as soon as possible and finding powerful foreign allies able to support their independence.
The factors taken into account when the Protector General decides who to attack is realm size, the greater the better, whether or not the lord is pillaging China, whether or not he has usurped Chinese Bureaucracy, and relative strength. Rulers with a Peace Treaty and Imperial Tributaries are not subject to Great Invasions.
Attacking the Western Protectorate for land
You can declare war on the Western Protectorate with regular CBs for land, such as the holdings in the North-East of Tarim Basin at the 769 start. This will deduct most (if not all) your current grace and will temporarily prevent you from interacting with China. After declaring war, China will send event troops on foot to Jiuquan or by ships to Bengal Bay. Taking land from the Western Protectorate does not require beating the event troops, as simply occupying the entirety of the Western Protectorate's on-map territory will give you 100% warscore.
The Western Protectorate can join Holy Wars as a defender for rulers of the same religion. This will lower the attacker's monthly grace and interrupt interaction, but will not result in Chinese event troops being sent out.