Before you start you should have the ninja at all levels at the maximum.
What for and why do you see in this video

Yt Vid: https://www.youtube.com/watch?v=pYzKc37UFGU (Btw The video is not mine)

There is a certain tactic with the ninjas.
With which you can master almost any map with difficulty

Yt Vid: https://www.youtube.com/watch?v=bxVQ-Sgc8so

Levels you need

Ninja in first level Maxed

Ninja at intermediate level 3 Shinobi tactics