22 Zero-Days A secret will work if it is kept; you will lose if words are given away.

You should be aware that you shouldn’t use any of the ancient ways that are known to people because you will lose the edge of surprise.

—Shōninki, “Takaki wo Koe Hikuki ni Hairu no Narai” 1

One of the shinobi’s key tactical advantages was secrecy. The scrolls repeatedly warn shinobi to prevent others from learning the details of their capabilities, since if knowledge of a technique leaked to the public, the consequences could be disastrous. Not only could the techniques be invalidated for generations, but the lives of shinobi using a leaked technique could be in danger. Both Shōninki and the Ninpiden describe the hazards of exposing secret ninja tradecraft ...

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