This was the German early version of 'Ilona', and as such a plan to be put into effect after the collapse of the USSR or after any British landing in the region, to secure bases in Spain and Portugal, as well as Dakar in French West Africa, primarily for the continuation of the maritime strangulation of the UK (5 September 1941/28 May 1942).
'Isabella' (i) was an early developmental version of a smaller-scale plan later called 'Ilona'. Much like the related 'Felix' (i), the plan called for invasion of mainland Spain, as well as the capture of Portugal and Spanish possessions in North and West Africa, Gibraltar and forward operating bases in the Canary, Azores and Cape Verde island groups. Unlike 'Felix' (i), however, 'Isabella' (i) was based on the assumption that the Spanish forces would at least be sympathetic to the Axis cause and that the invasion of Spain proper would be started only with the help of the Spanish should Allied forces land on the Iberian peninsula. To secure the southern flank of the operation, the German forces were also to take the Vichy French port of Dakar in West Africa.
The implementation of the plan was clearly beyond the capabilities of Germany at the time it was conceived, despite the comparative weakness of the UK in this period, but if successfully implemented would have given Germany a commanding strategic position in the Atlantic and West Africa to hinder the movement of British convoys across the Atlantic and also to and from the Middle East and India via the Cape of Good Hope.
Although the plan was never put into force, a forward logistics base for the invasion was prepared in Bordeaux.