Ad: This forum contains affiliate links to products on Amazon and eBay. More information in Terms and rules
The Soviets acquired a F-5E along with other former South Vietnamese aircraft that were shipped to the USSR in 1975. They tested and flew the F-5 extensively and were very impressed with it. There is a several page narrative of these tests in 'US Aircraft in the Soviet Union and Russia' by Gordon and Komissarov.
I understand the F-5 performed well in Red Flag and Top Gun, even against advanced fighters like the F-15 and F-14. Small size and difficult to see along with agility, and of course, expert pilots, really called into question the advantage of few-of-quality verses many of capable quality theory the Services had.
Certainly the mentality of the AF and Navy in the 50s and 60s was away from purpose built dogfight type aircraft like the F-5 and F-8, including training, and more to the do everything reasonably well F-4, which led to a big surprise in Vietnam.
I understand the F-5 performed well in Red Flag and Top Gun, even against advanced fighters like the F-15 and F-14. Small size and difficult to see along with agility, and of course, expert pilots, really called into question the advantage of few-of-quality verses many of capable quality theory the Services had. The Navy, of course, always had to deal with limited deck space and needed multipurpose aircraft.
The book I mentioned above also has great photographs of the F-5 in the air and on the ground in Soviet markings.