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 actually continued on in a very 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 theory 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 would write, “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 noted that some of “ATIC’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.”

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.”

Critics charged that, from its formation, Project Grudge was operating under a debunking directive: all UFO reports were judged to have prosaic explanations, though little research was conducted, and some of Grudge’s “explanations” were strained or even logically untenable. In his 1956 book, Edward J. Ruppelt would describe Grudge as the “Dark Ages” of USAF UFO investigation.

Grudge personnel were in fact conducting little or no investigation, while simultaneously relating that all UFO reports were being thoroughly reviewed. Ruppelt additionally reported that the word “Grudge” was chosen deliberately by the anti-saucer elements in the Air Force.