Prelude: The Fated Night
Prelude: The Fated Night
Prelude: The Fated Night
It was the night of December 23th, 1673 when the Forbidden City burned.
During the Qing conquest of China, many Ming generals defected to Great Qing due to various reasons. These defecting generals, called Xiangjiang(降將), were treated with high respect and courtesy by the Qing, and were often rewarded with esteemed positions. These xiangjiangs defected along with their troops, and had knowledges about the local conditions - making them a valuable asset.
Of these xiangjiangs were a general named Wu Sangui(吳三桂). After Ming's crushing defeat at the Battle of Songshan(松山) and Beijing falling to Li Zicheng(李自成)'s peasant rebellion, Wu's army was left defending the Shanhai Pass(山海關) - The stronghold separating mainland China and Manchuria. Both Li Zicheng and Great Qing wanted to persuade Wu and his forces to defect to their side. Initially, Wu agreed with Li Zicheng to unite against the invading Manchu army. However, the cooperation fell apart, and with a gargantuan Qing army approaching the pass, he opened the gates for the Manchu forces in May 1644, beginning the Qing conquest of mainland China. 
△Portrait of Wu Sangui.
As the Qing pushed further into China, they were met with fierce resistance of the South Ming regime. The rugged landscape of southern China hindered the mobility of the Manchurian cavalry, and the Ming populace was fully loyal to the southern government. As a solution, instead of the Manchu and Mongol Bannermen, the Qing put xiangjiangs and their Han armies in charge of conquering the south.
Xiangjiangs like Wu proved their worth during the conquest of southern China. Wu Sangui was especially ardent in his efforts - he tracked the fleeing Yongli Emperor and his family all the way to Burma, and historians say that he strangled every single one of the family member himself.
After South Ming collapsed, the Qing court crowned these defectants as Fanwang(藩王: Feudatorial Kings), and let them rule over the territories they have conquered. A total of three xiangjiangs - Wu Sangui, Shang Kexi(尙可喜) and Geng Zhongming(耿仲明) were crowned, each as Pingxiwang(平西王: King of the Pacification of the West), Pingnanwang(平西王: King of the Pacification of the South), and Jingnanwang(靖南王: King of the Stabilization of the South).
However, as time passed by, Qing government became more weary with the Feudatories. An autonomous Han state within the empire, with its own army and bureaucracy served as a threat to Qing rule in China. The Feudatories were making enormous tax gains by dominating the regional trade, and raising their own armies that could be used against the Qing in a possible revolt. Of the Three Feudatories, Wu was the most influential. Wu used his own currency in his realm, and deeply interfered with Qing rule in the broader Southwest - to the point where Wu's opinions arguably mattered more than that of the Qing court.
When young Aisin Gioro Hiowanei assumed control of the Empire as Emperor Kangxi(康熙), he was determined to strip power from the Feudatories. The opportunity came when in 1673, Shang Kexi asked for permission to retire and succeed his position to his son Shang Zhixin(尙之信). Emperor Kangxi permitted his retirement, but rejected the succession to his son - the title of Pingnanwang was to be abolished, and his realm returned to Peking.
This put Wu Sangui and Geng Jingzhong(Grandson of Geng Zhongming, Jingnanwang at the time) on alert. In July of the same year, they also asked for retirement, testing the waters to prepare for further action. The Qing court was divided on the reply, for taking the hard line and fully abolishing the Feudatories could result in an all-out insurgency in the south. But Kangxi was confident and determined, and decided to generously ‘grant’ them their request, with the same conditions.
After hearing the reply from Peking, Wu's advisors and lieutenants alleged that it was finally time to rise and overthrow the Manchurian rule. Wu was also determined to walk the warpath. In November of 1673, after failing to persuade him to join the rebels, Wu Sanggui’s forces killed Zhou Guozhi(朱國治), Governor-General(巡撫) of Yunnan, marking the beginning of the War of the Three Feudatories. Gan Wenkun(甘文焜) , Viceroy of Yun-Gui(總督: Yunnan and Guizhou), tried to take control of the situation and snuff out the rebellion, but he found the governors and generals of Yunnan were loyal to Wu.
Wu Sangui claimed the cause of his rebellion to be "Opposition to Qing and Restoration of Ming(反淸復明)", although his sincerity was questioned because of his previous acts as a Xiangjiang. He also urged other Feudatories and regional governors to join his rebellion. On the other hand, Emperor Kangxi revoked the abolishment of the Feudatories in an attempt to satiate the Feudatories and stop them from joining the rebellion.
△An overview of the Forbidden City.
Wu Sangui’s son, Wu Yingxiong, had been staying in the Forbidden City as the emperor’s guest and potential hostage when the war began. After his father’s treason against the Qing, Yingxiong fell to a precarious position, and felt the need to escape the city before he was executed by the court.
In December of 1673, there was a man in Peking named Yang Qilong(楊起隆). He had been claiming himself to be the ‘Zhushan Taiji(朱三太子)’ - the “Third Prince of the Zhu”, the third son of the Chongzen Emperor and the rightful heir of the Ming. Gathering followers of him in and around Beijing, Yang plotted a conspiracy to raise ten thousand soldiers to raid and burn the Forbidden City, kill the false emperor, and restore the Ming Dynasty.
Raising such a force right at the center of the empire without the empire noticing was not an easy task, but Yang managed to prepare for the plan without getting compromised.  Yang also got in contact with Wu Yingxiong - Wu provided Yang with classified intels of the court, which Yang could use to his advantage. In return, Yang promised safety of Wu and his family, so that he could utilize the chaos of the revolt to flee from Beijing.
At December 23th, commanded by Zheng Desheng(鄭得勝), Yang’s insurgents began setting fire all around Beijing. Although Beijing had a large garrison of Bannermen soldiers guarding it, they had been occupied with preparing for a expedition to the south, and the element of surprise hindered their initial reaction.
Taking advantage of the chaos, Yang Qilong led his own army and attacked the Forbidden City, to kill Emperor Kangxi. Although he was met with fierce resistance from the elite Imperial Guard(禁軍), and most of the men he led were killed in action, Yang managed to achieve the main objective of the incursion - death of the false emperor. An unknown soldier managed to impale and kill Emperor Kangxi, beheading the Qing Empire.
As hours passed and more parts of the city discovered the Emperor’s murder, the administration fell into total disarray. Meanwhile, the rebels continued to storm the capital. Chen Yi(陳益), leading 50 rebels alongside him, managed to track and kill Tu Hai(圖海), the Du Tung(都統, commander) of the Zheng Huangqi(正黄旗) - one of the Eight Banners.
However, as morning dawned, the Qing garrison began to gather themselves. With Tu Hai dead, Zu Yonglie(祖永烈) assumed command of the Zheng Huangqi garrison and led a counter-attack against the rebels. The Xiang Huangqi(鑲黃旗) and other stationed armies also joined forces. After a day of fighting across the streets, the winner of the battle for Beijing had turned evident; The rebels, completely outmatched by the Qing army in a proper battle, were crushed by the Eight Banners. Yang Qilong, Chen Yi, Huang Ji(黃吉) and even Wu Yingxiong himself were killed in action. However, Wu’s sons were able to escape Beijing, fleeing south to their grandfather’s lands.
Although order prevailed in Beijing, it was evident that the damage was irreversible. With the emperor and his finest servants dead, and the countryside burning in revolt, it seemed there was nothing but darkness ahead for the young empire.
After a year or so of lurking in the site, I have finally decided to post my own Timeline.
The PoD is that Emperor Kangxi dies prematurely, leading to a successful Revolt of the Three Feudatories. This TL was originally planned as a Korea-wank, but the scope of the TL widened until it wasn't really a 'Korean TL' anymore - Still, Korea would probably receive a lot of spotlight during the course of this TL .
Feedbacks are welcome!
 There are various explanations, some less credible than others, for the exact reason why Wu defected to Great Qing. Some suggest Wu was appalled by the barbarianism displayed by Li's rebellion when it sacked Beijing, while others state lover shenanigans or other explanations. Here, we will leave it underexplained on purpose.
 IOTL, the plan was found out in December 21th, two days before its execution, and the conspiracy was crushed by the Beijing garrison. Yang fled to the countryside - only to be caught in 1680 in Shanxi and executed. This is the PoD of TTL and OTL.