Although they cannot be classed as Republic production aircraft, the Thundermirage, as these decoys came to be called, was an attempt to create the illusion of a larger air force than actually existed. This was not a new idea; wooden decoy aircraft were use in WWI, and inflatable decoy aircraft were used in WWII. Also, the Bell XP-59 was disguised during some of its first appearances by addition of a fake propeller. Belgium used several F-84F aircraft as decoys by modifying them to appear as Mirage V aircraft. Modifications included removing the horizontal tails, adding Mirage-style fake intakes, and adding a pointed Mirage-style nose over the F-84 intake. Inspection of the photographs shows the modifications were not consistent from one aircraft to another. The F-84 series endured a wide variety of testing and other experimental use in its lifetime. No doubt, the Thundermirage was one of the more unusual uses of the F-84.
About the F-84F Thundermirage decoys
The ex FU-192 and ex FU-194 photos were both taken at Beauvechain (an F-16 base) in May 1986. The wings were given a "Delta"(ala Mirage V) look using plywood. Untill 1979 I know these were all painted in the so-called VietNam camo scheme, but with arrival of the F-16 FU-194 was given a Grey/Blue scheme, but no other changes. most Belgian bases had about eight to ten of these decoys placed on various spots on the airfield.