The letter from the U.S. government explained that an internal investigation had reviewed documents back as far as 1958 and that the documents disclosed that nuclear weapons were present at Thule Air Base on two occasions. The first introduction occurred in February 1958 when four airborne weapons and 15 non-nuclear components were deployed. The bombs were returned to the United States about eight months later. The second introduction began in December 1959, and consisted of 48 air defense weapons. These weapons remained in place until the summer of 1965 when they were returned to the United States as the U.S. Army canceled its air defense program at Thule Air Base. After the summer of 1965, the letter explains, the United States has not deployed nuclear weapons in Greenland.

Mindful of the sensitivity of the matter, the letter warns that disclosure of the information could seriously affect U.S. foreign relations. "If this information, or part of it, should be made public," the letter warns, "the U.S. government will neither confirm nor deny its validity." (Subsequent FOIA requests to the U.S. government for this letter continue to go unanswered).

Despite the letter's sensitivity, the details were disclosed by the Danish government in various public statements in 1995 and 1996. Moreover, the text of the letter was subsequently leaked to the press by a source in the Danish government. An unofficial version of the letter is available for downloading in the right-hand bar.

Although the letter does not specify the types of the warheads, the U.S. Air Force has since disclosed the specific bomb types deployed at Thule (click here).