Combat application: Hiding your motion in motion. Example; light hopping in sparring can hide your attack."
What it means:
If you want to carry out a secret ploy or mission, you got to keep the suspicion of your target at a minimum. Common sense! So how do you minimize suspicion? By creating an environment of familiarity and normality!
One fantastic example of this is the movie "Ocean's Eleven" and its sequels. In order to carry out their grand plan, everyone goes undercover and pretends to be very normal guests and workers. In fact, "Ocean's Eleven" movie title in China is translated into "瞒天过海", the very title of this stratagem.
Applied to KW:
One direct example of how this can be applied is to keep both your characters hidden once you know you are one of the minority kingdoms or an Ambitionist. "Go along" with the minority players and feint an alliance, strike the majority kingdom first. You could even latch unto a minority kingdom and support this kingdom vigorously, building the impression that you belong to the same kingdom. Secretly, build up your strength in preparing to backstab your temporary ally.
An alternate version is to remain the last player with both characters hidden, whilst already knowing you belong to the majority kingdom. Be sure to do the math carefully to ensure you don't end up as Ambitionist. Bite unto one minority kingdom and concentrate your firepower there, whilst tricking another minority kingdom into thinking you could be on their side. This serves to provide an illusion of balance of powers and prevents the minorities from forming a strong coalition out of fear.
Overcoming this Tactic:
The use of "Ascertain 知己知彼" tool card is critical here. That is the sure-fire way to determine the allegiance of players with both characters hidden.
Historical Basis of this Stratagem (from Wikipedia):
This stratagem references an episode in 643 AD, when Emperor Taizong of Tang, balked from crossing the sea to a campaign against Koguryo. His general Xue Rengui thought of a stratagem to get the emperor across and allay his fear of seasickness: on a clear day, the emperor was invited to meet a wise man. They entered through a dark tunnel into a hall where they feasted. After feasting several days, the Emperor heard the sound of waves and realised that he had been lured onto a ship! General Xue drew aside the curtains to reveal the ocean and confessed that they had already crossed the sea: Upon discovering this, the emperor decided to carry on and later completed the successful campaign.
This stratagem means that you can mask your real goals, by using the ruse of a fake goal that everyone takes for granted, until the real goal is achieved. Tactically, this is known as an 'open feint'; in front of everyone, you point west, when your goal is actually in the east. By the time everyone realised it, you have already achieved your goal. Harro von Senger notes in the German-Language "Die List" that to grasp the full meaning, it would be something like "to deceive the holy virgin Mary" in the West.
This stratagem makes use of the human failing to become unaware of common everyday activities, or events that appear normal. The best secrets are carried out in broad daylight. The best hoax is to repeat it so often that people are convinced that the next move is also a hoax. When this happens, it is the best moment to carry out one's previously hidden true objective.