It is based on an assumption
that three united arrows would be difficult to be broken off
even though an arrow is easy to be broken off.
Approximately 400 years ago,
when a lot of "Provincial Wars general "existed in Japan,
Mouri Motonari, who was a famous general in Aki area,
explained this lesson for His three sons.
Then it has become one of family precept of Mouri clan.
Provincial Wars general: Sengoku Daimyo in Japanese
Three present arrows:
Three arrows are used as a figure of speech of
three policies at present.
Three arrows which are Japanese political policy
and root of common name Abenomics are the representative example.
However, it is the current state that the reality of Abenomics
is "not" understood by a lot of people well.