Project Grudge was a short-lived project by the U.S. Air Force to investigate unidentified flying objects (UFOs). Grudge succeeded Project Sign in February, 1949, and was then followed by Project Blue Book. The project formally ended in December 1949, but continued in a minimal capacity until late 1951.
Project Sign had been active from 1947 to 1949. Some of Sign's personnel, including director Robert Sneider, favored the extraterrestrial hypothesis as the best explanation for UFO reports. They prepared the Estimate of the Situation arguing their case. This hypothesis was ultimately rejected by high-ranking officers, and Project Sign was dissolved and replaced by Project Grudge.
It was announced that Grudge would take over where Sign had left off, still investigating UFO reports. But as Air Force Captain Edward J. Ruppelt wrote, "In doing this, standard intelligence procedures would be used. This normally means an unbiased evaluation of intelligence data. But it doesn't take a great deal of study of the old UFO files to see that standard intelligence procedures were not being followed by Project Grudge. Everything was being evaluated on the premise that UFOs couldn't exist. No matter what you see or hear, don't believe it." (Ruppelt, 59-60, emphasis his)
Ruppelt noted that some of "ATIC's Air Technical Intelligence Center's top intelligence specialists who had been so eager to work on Project Sign were no longer working on Project Grudge. Some of them had drastically and hurriedly changed their minds about UFOs when they learned the Pentagon was no longer sympathetic to the UFO cause." (Ruppelt, 60)
As Dr. Michael D. Swords writes, "Inside the military, Maj. Aaron J. Boggs in the Pentagon and Col. Harold Watson at AMC Air Material Command were openly giving the impression that the whole flying saucer business was ridiculous. Project Grudge became an exercise of derision and sloppy filing. Boggs was so enthusiastically antisaucer that General Cabell ordered General Moore to create a more proper atmosphere of skeptical respect for the reports and their observers." (Swords, 98)