In the Yongzheng Dynasty, Kangxi must have known of Wu Sidao's existence.
In the "Yongzheng Dynasty", although Kangxi lived deep in the imperial palace, the dynamics of the official field and the city can still be understood in great detail. On the one hand, it was the mutual impeachment of officials and the mutual reports of the princes that enabled him to understand the development of the situation without leaving his home; on the other hand, Kangxi attached great importance to the work of "espionage," especially when Kangxi was "chasing after the arrears of the household department," and he was able to learn in detail about the illegal behavior of a large number of corrupt officials who perverted the law, which showed the severity of this spy force, not to mention that during the Kangxi period, a system of secret folding and special performance had already been established, and spies and eyes and ears had already begun to be installed in various places. Therefore, Kangxi was able to grasp and understand some trivial issues in a timely manner to a large extent.
Especially during the "Nine Sons and Concubines", the princes were tit-for-tat, and they had reached the point where water and fire were intolerable, and the most threatening and insecure of them was the Kangxi Emperor himself, so it was impossible for him not to grasp and control the dynamics of the princes, so the existence of Wu Sidao could not be unaware, especially Yongzheng wanted Wu Sidao to serve as a teacher for Hongli and others, and put on a grand display, which would make Kangxi know.
In fact, it was not just Kangxi, even if the fences on the Yongzheng Mansion were firm and strictly managed, there was no impermeable wall, and the existence of Wu Sidao was actually not a secret.
Despite this, there are always very few people who really know wu Si Dao's abilities and roles.
Wu Sidao did not know much about the role and significance of Yongzheng, and only the thirteenth master, Nian Qianyao, Li Wei, Gao Fu, and Gao Wuyong knew about it, and even Yongzheng's Fujin said that he was just a "doorman who ate white food", so it can be seen that even she did not know.
First of all, it is because Wu Sidao has made a very good cover with the identity of the teacher of Hongli and others.
Yongzheng's sons reached the age of study, and it was no wonder that they should ask for a teacher for the children, and Wu Sidao was indeed trying to educate Hongli and others during the day instead of thinking about it, so from Yongzheng's own mansion up and down to the external instructions, Wu Sidao had always been described as a teacher of Hongli and others, and used this identity as a cover.
Secondly, the time when Yongzheng and Wu Sidao discussed things was either at the dinner table or in the middle of the night, and the only people involved were Yongzheng, the Thirteenth Master, and Wu Sidao.
Yongzheng's secrecy work for Wu Sidao is actually very good, especially when Wu Sidao just entered the house, Yongzheng and Wu Sidao were talking late at night, and the participation of the thirteenth master was also a later thing, and it was precisely because of Yongzheng's very good secrecy means and secrecy work that the outside world did not know what Wu Sidao really did.
Third, it was Gao Fu's death that completely eliminated the possibility of Wu Sidao's identity leaking.
Yongzheng killed Gao Fu, not only because of Gao Fu's betrayal, nor just because Gao Fu sent the prince's letter to Brother Ba, Yongzheng wanted to kill him to kill him, and there was another layer of meaning, that is, to cover up Wu Sidao's identity, and not to let Wu Sidao's true identity be made public.
After all, Gao Fu knew everything in the Yongzheng Mansion, and it was Wu Sidao who directly instructed and arranged for Gao Fu to do things, so Yongzheng could only kill Gao Fu and cover up this secret in order to completely cut off such a possibility.
Therefore, it is precisely because of Yongzheng's efforts to cover up and to achieve the ultimate secrecy as much as possible, although the existence of Wu Sidao is already known, the real role of Wu Sidao and its value to Yongzheng are not known to outsiders, including the Kangxi Emperor.
The historical Wu Sidao did not know the Yongzheng Emperor before Yongzheng ascended the throne.
The historical Wu Sidao was an aide to Tian Wenjing's palace, and it was Wu Sidao who saw Yongzheng's thoughts and took the initiative to suggest that Tian Wenjing impeach Longkeduo, thus opening the prelude to the fall of Longkeduo, and Wu Sidao was also known to the Yongzheng Emperor at this time under the recommendation of Tian Wenjing, and Yongzheng also expressed his respect for Wu Sidao by greeting Tian Wenjing with "Mr. Wu is safe".
And these all happened after Yongzheng succeeded to the throne, before Yongzheng succeeded to the throne, he did not know Wu Sidao, so Wu Sidao was an important strategist and a first meritorious minister who helped Yongzheng ascend to the throne, these are just the interpretation of TV dramas, but there is no such thing in history.