Project Grudge soon followed, which in turn was replaced by Project Bluebook.

Project Sign was dismantled and became Project Grudge at the end of 1948.

This evolved into Project Grudge (1949-1951) and then Project Blue Book (1952-1970).

Project Grudge became an exercise of derision and sloppy filing.

Project Grudge issued its only formal report in August 1949.

By the time Project Blue Book supplanted Project Grudge, the changeling was looking elsewhere.

Project Sign was succeeded at the end of 1948 by Project Grudge, which was criticized as having a debunking mandate.

Blue Book was also upgraded in status from Project Grudge, with the creation of the Aerial Phenomenon Branch.

By late 1948, Project Sign was discontinued in name and replaced by a much more negatively oriented Project Grudge.

Project Grudge was replaced with Project Blue Book in early 1952.