The German operational planning against Switzerland consisted of four main attack plans. For an overview see the planning timeline.
Interestingly enough, the plans made by the OKH (26.6., 12.8. and 9.10.) asked for 9 to 11 divisions. Planners with 12th army and Army Group C always asked for significantly more divisions (mainly infantry). Especially the later plans asked for significant number of engineering units (between 24 and 49 batallions).
German intelligence was not very good at recognizing the shift of the Swiss army from their positions in June 1940 (see Operationsbefehl 10) to the central redoubt. Even the last plan in October 1940 still assumed, that the main body of the Swiss army could be brought to battle in the Swiss plain and not in the mountains.
Based on this (faulty) intelligence all German operational planning was based more or less on the same operational idea:
(click here to get a large version of the graph in a new window)
Summary of the Plans
The first plan was finished on 26. June 1940, the day the armistice with France took effect. A large number of forces were available to the Germans to put the plan into execution with a short delay. A second plan, which was the refinement of the first one was elaborated mid August 1940. Both plans were prepared by Hauptmann von Menges of the operations section of the OKH for the 12th Army.
Both plans asked for 9 divisions (+1 in reserve) to complete the task (1 Panzer, 3 motorized , 1 mountain, 5 infantry) and two motorized infantry regiments in 3 corps.
End of August 1940 the HGr C submitted a third plan requiring 24 divisions.
In October 1940 a fourth plan was prepared by Major Zimmermann . The plan asked for 21 divisions (2 panzer, 4 motorized, 2 mountain, 3 infantry), one motorized infantry brigade and five mountain pioneer batallions in 3 corps for the sector of 1st army only. The OKH stripped down the number of divisions to 11.
[Last Update 30.08.2010]