A 1968 letter from Defense Secretary Clifford to State Secretary Rusk
at http://www.state.gov/r/pa/ho/frus/jo...b/xii/2262.htm mentioned
that the air bases in Spain were originally built for SAC operations
and some B-58 bombers and accompanying tankers were earmarked for
forward deployment there.

How many refuels were needed for a fully-laden B-58 to bomb its target
in the USSR and come back to Spain?

On a side note, Vice Admiral Gerald E. Miller wrote in his book
"Nuclear Weapons and Aircraft Carriers" that the Navy RA-5C Vigilantes
- operating from carriers in the Bay of Biscay - were assigned to
targets in Eastern Europe.