What Trainings did ancient ninja go through?

The original training of the ninja before the stealth was added was taught in the same places where the samurai was taught. This training can be traced back to China originally but it was modified. The ninja originally were people that didn't complete the training of the samurai or they were kicked out for breaking the Bushido code.

Later they added the art of stealth to aid them in their assignments and survival. Many became ninja out of necessity. It was a way to earn money and to support themselves.

Revenge motivated others. They were upset because they were removed from training to become samurai. They were highly skilled fighter but most of them didn't have the skill to compete with samurai in a fair fight.

They were hired assassins, mercenaries, and kidnappers. They could be hired by anybody with a cause. Yes they fought against the samurai.

But that was just a small part of what they did. They were used to influence certain laws to be changed or not changed. They could cause ... more.

I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.