The top secret operation, code-named "Project Seal", tested the doomsday device as a possible rival to the nuclear bomb. About 3,700 bombs were exploded during the tests, first in New Caledonia and later at Whangaparaoa Peninsula, near Auckland.
The plans came to light during research by a New Zealand author and film-maker, Ray Waru, who examined military files buried in the national archives
"Presumably if the atomic bomb had not worked as well as it did, we might have been tsunami-ing people," said Mr Waru. "It was absolutely astonishing. First that anyone would come up with the idea of developing a weapon of mass destruction based on a tsunami ... and also that New Zealand seems to have successfully developed it to the degree that it might have worked."