In Mein Kampf, Hitler had imagined that Britain would be an ally in the west against France, and so the strategy vaguely laid out in that book does not contemplate an enduring war in the west.
In Mein Kampf, Hitler had imagined a short war against France, and then the conquest of the USSR. He had wrongly assumed that Britain would be an ally in the west against France, and so he did not foresee an enduring war in the west.