fascism wouldn't contain this qualification.
Fascism thinks their cause is just. It's why for example Hitler didn't want to fight Britain. He didn't view it as a just war since England too was an Aryan nation in his view. While it would be horrible to contemplate, I think Hitler would have been quite willing to not only negotiate a peace with Britain after the Fall of France, but also to honor it. Whether his successors would have is a different matter.
My understanding is that Hitler wanted Britain to come under Nazi rule to become part of the Aryan dominion, but would have preferred to do it without war against them. The justice of the cause was considered a given because there was no higher law beyond the interest of the Aryan nation, and the Nazi regime embodied that interest.