If he defied Hitler and did not destroy Paris before the Allies arrived, his family of a wife and three children living in Baden Baden would fall under the rule of Sippenhaft–they would be punished for his failure to obey orders and could possibly be executed.
Underland: A Review
To experience the Underland, he survives blizzards, freezing water, ice crevasses, blocked cave passages, and oxygen deprivation.