The conventional submarine fleets least welcome as opponents

Which present-day non-nuclear submarine fleet would be the most difficult opponent?

Japan is selected for the number and quality of its submarines, with Italy and Sweden receiving honourable mentions.

Japan is the first choice because it combines a large submarine fleet with high-quality boats. Italian and Swedish submarine forces also receive favourable assessments. Sweden's submarines are considered particularly formidable in their own waters, a judgment shared by the participants. Japan ranks first among the non-nuclear submarine fleets discussed.