Russia was indeed considered a threat to New Zealand, and the rest of the former British Empire. Whether or not the threat was real, the fear was definitely real hence the fortifications.

Whilst a hoax article can be cited as the start of the fear, there are some incidents such as the Confederate ship Shanendoah docking in Australia on the way to attacking whaling ships off Alaska and the Russian warship Gaidamak leaving Melbourne heading west which left New Zealanders feeling part of the world-wide theatres of war, our isolation being no defence in itself.

One could conclude that it was the cynical use of fear among the citizenry to sell arms by British manufacturers throughout the British Empire as Australia is dotted with similar gun emplacements.

Was the threat of Russian invasion real? Probably not, but I would compare it to the more recent Cold War fear of Russian nuclear missiles hitting New Zealand. In both instances it was technically possible, hence the fears were real.