It envisaged a German Army attack targeting the Allied forces in eastern Belgium and Luxembourg, east of the Meuse River.
Herbstnebel was created as an alternative to Wacht am Rhein, Adolf Hitler's plan to seize Antwerp and bottle up all Allied forces in Belgium and the Netherlands.
Model, along with all the other senior commanders involved, believed this was unachievable given Germany's limited resources at the time.
Like Wacht am Rhein, Model's attack would be launched in the Ardennes sector, but would then turn north instead of continuing west and northwest.
Confusingly, Operation Wacht am Rhein was itself renamed Herbstnebel in early December, although it remains most well known by its original name.