The history of the Ninja is hard to trace. This is because there were few, if
any records kept of its existance. Most of what is known about the ninja is
taken from stories that have been passed down from generation to generation.
Nonuse ("the art of stealth") was first introduced to Japan in 522 A.D. as a
religion practiced by priests. These priests were not violent people, they were
"mystics" who gathered and shared information for the ruling classes. The ninja
as we know them were not introduced until later.
It wasn't until 645 A.D. that the priests perfected their fighting skills and
made use of their knowledge of nonuse. This was because they found themselves
being harassed by the central government and found in necessary to protect
themselves.
In 794-1192 A.D. the new civilization flourished and with it, a new class of
wealthy, privileged families. These families fought with one another in attempts
to make or destroy emperors. The need for spies, informants and now assassins
grew as these families dueled for power. They were suspicious and jealous of one
another and would resort to any means necessary to eliminate any possible
threats. Therefore, the practitioners of nonuse were in great demand. With this,
the ninja was born.
As the ninja gained popularity, so did the stories of their superhuman
abilities. This reputation was often encouraged by the ninja themselves. Because
they were a relatively weaker people then their counterparts, the samurai, and
were vulnerable to attack by the many warring families around them, it was to
their advantage to have others believe they had such powers. Powers like having
the strength of ten men, ability to turn into animals, fly and become invisible
at will. The ninja movies also added to the abilities by having the ninja jump
over buildings in a single jump, catch bullets in their teeth and see into the
future.
At this point you must understand the samurai to truly understand just why the
ninja were so effective and in such demand. The samurai's life was to "live by
the sword, die by the sword", with no fear of death at all. His sword was his
whole life, his soul. With this he followed the warriors code of honor, the
Bushido. The bushido was to be followed at all times. If a samurai were to stray
from the code he would then commit seppuku, another term for hara-kiri. This was
a ritual suicide where they would cut their stomach open with their smaller
sword.
The ninja followed no such code. Their only code was to do whatever it takes to
get the job done. This gave the ninja a great advantage right away, add the use
of a wide variety of weapons and you have a superior warrior. Since the samurai
could not sneak into an enemy's house, because it was against their code, they
could not carry out such tasks as assassination and sabotage. This is where the
ninja came in. And if that meant sneaking up behind a samurai warrior and
killing him before he even knew he was in danger, that was very permissible by
the ninja. The bushido would never allow for this. For this reason the samurai
were afraid of the ninja. A fear the ninja had earned.