Western Sahara Joins Morocco in 1955
The sine qua non of the transfer of the Western Sahara from Spain to Morocco would have been a change in the attitude of the Franco regime. After all, it was Franco's desire to retain the remnants of the Spanish Empire that led him to devote considerable resources to the retention of that territory.
This change in attitude could be the result of:
1. The death of Franco.
2. A deal between Spain and Morocco that traded the Western Sahara for guarantees of continued Spanish control over it's enclaves in North Africa.
3. A shift in US policy that made US support for Spain contingent upon the transfer of the Western Sahara to Morocco. (This, in turn, might have been a product of a somewhat different attitude towards the FLN in Algeria and Arab Republicanism in general.)