  Using the embedding tensor formalism we give the general conditions for the
existence of N=1 vacua in spontaneously broken N=2 supergravities. Our results
confirm the necessity of having both electrically and magnetically charged
multiplets in the spectrum, but also show that no further constraints on the
special Kahler geometry of the vector multiplets arise. The quaternionic field
space of the hypermultiplets must have two commuting isometries, and as an
example we discuss the special quaternionic-Kahler geometries which appear in
the low-energy limit of type II string theories. For these cases we find the
general solution for stable Minkowski and AdS N=1 vacua, and determine the
charges in terms of the holomorphic prepotentials. We find that the string
theory realisation of the N=1 Minkowski vacua requires the presence of
non-geometric fluxes, whereas they are not needed for the AdS vacua. We also
argue that our results should hold in the presence of spacetime and worldsheet
instanton corrections.
