I would like to know (from the beginning to the end of the war) what steps I must follow to have the neutral ending, help please

There exists a guide in the game page. It is updated to v 0.19 but it details what you need to do to be on the good / neutral route.

Here's the guide : https://docs.google.com/document/d/1HjgBoSAq4659ANHfDyhqaSqqgL9fdVHKBp3hZ2-auUE/...