三十六计 Thirty-Six Stratagems: 瞒天过海 Fool the Emperor to Cross the Sea
Chapter 1: Winning Stratagems 胜战计
This stratagem references an episode in 643 AD, when Emperor Taizong of Tang (唐太宗 tánɡtàizōnɡ), balked from crossing the sea to a campaign against Koguryo. His general Xue Rengui (薛仁贵 Xuē Rénɡuì) 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' (声东击西 shēnɡdōnɡ-jīxī); 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 (骗局 piànjú) 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.