Primary Sources: Permissive Action Links and the Threat of Nuclear War

_In his post “Almost Everything in ‘Dr. Strangelove’ Was True,” Eric Schlosser describes how closely the events in Stanley Kubrick’s movie mirrored what could have actually happened to America’s nuclear arsenal. See his comments on clips from “Dr. Strangelove” and from a little-seen film about nuclear-weapon safety. In this post, he looks at the long-secret documents that help explain the risks America took with its weapons.

Permissive action links (PALs) are the coded switches installed in nuclear weapons to prevent them from being used by rogue officers, madmen, terrorists, and saboteurs. Until the mid-nineteen-sixties, few of America’s nuclear weapons contained a locking device. Anyone who got hold of a weapon might be able to detonate it. The introduction of PALs was intended, among other things, to reinforce Presidential control over the nuclear arsenal of the United States. The documents below were obtained through a variety of means: my own Freedom of Information Act searches; public archives; the Web site of Steven M. Bellovin, a professor in the Computer Science department at Columbia University; and the National Security Archive, based at George Washington University, which for decades has been obtaining important government documents and making them available to the public.

  1. This 1961 letter from a State Department legal adviser addresses the issue of whether to put permissive action links in NATO’s nuclear weapons. The letter refers to a study by Dr. Marvin Stern, a Pentagon scientist, who’d urged the adoption of some sort of locking mechanism. The State Department strongly supported such a move, while the Joint Chiefs opposed it.

State Department on PALs (PDF) State Department on PALs (Text)

“Subject: Atomic Stockpile, Letter, From John H. Pender, Legal Adviser, Department of State, to Abram J. Chayes, Legal Adviser, Department of State,” July 16, 1961 (TOP SECRET/declassified), National Security Archive.

  1. President John F. Kennedy’s science adviser, Jerome Wiesner, was a strong proponent of PALs. In a memo to the President dated May 29, 1962, Wiesner advocates the use of PALs—but warns that they can be easily disabled and won’t entirely solve the problem of unauthorized use.

Wiesner to J.F.K. (PDF) Wiesner to J.F.K. (Text)

Appendix A, NSAM-160 and Wiesner Memorandum, in “PAL Control of Theater Nuclear Weapons,” Mark E. Bleck and Paul R. Souder, Command and Control Division, Sandia National Laboratories, SAND82-2436, March, 1984 (SECRET/FORMERLY RESTRICTED DATA/declassified).

  1. One week after receiving Wiesner’s letter, President Kennedy issues a National Security Action Memorandum ordering the use of permissive action links in all NATO nuclear weapons.

J.F.K. NSAM (PDF) J.F.K. NSAM (Text)

National Security Memorandum No. 160, “Permissive Links for Nuclear Weapons in NATO,” June 6, 1962 (SECRET/RESTRICTED DATA/declassified), John F. Kennedy Presidential Library and Museum.

  1. A year before the release of “Dr. Strangelove,” at a meeting of top Pentagon and State Department officials, Secretary of Defense Robert S. McNamara admits to being extremely concerned about the risk of accidental nuclear detonations and even an accidental nuclear war. The Berlin Crisis and the Cuban Missile Crisis have persuaded him that the President of the United States should be the only person with the authority to order the use of nuclear weapons. McNamara opposes delegating that power to military commanders, under any circumstances. Secretary of State Dean Rusk seems equally worried about the possibility of an accidental or unintentional nuclear detonation. But others at the meeting think that military commanders should retain the authority to use nuclear weapons delegated to them a few years earlier by President Eisenhower.

State-Defense meeting (PDF) State-Defense meeting (Text)

“Memorandum of Conversation (Uncleared), Subject: State-Defense Meeting on Group I, II, and IV Papers,” January 26, 1963 (TOP SECRET/declassified), National Security Archive.

  1. In May, 1964, months after “Dr. Strangelove” first appeared in theatres, the Air Force was still battling Secretary of Defense McNamara’s efforts to install mechanical devices to prevent the unauthorized use of nuclear weapons, and thereby regain civilian control of the America’s nuclear arsenal. In this telegram, General Thomas Power, the head of the Strategic Air Command, argues that putting a PAL-type coded switch on his Minuteman missiles will gravely threaten America’s national security.

Thomas Power telegram (PDF) Thomas Power telegram (Text)

“Cable, To General Curtis E. LeMay, From General Thomas S. Power, February 17, 1964 (SECRET/declassified), National Security Archive.

  1. This is an official history of permissive action links and other nuclear-weapon command devices that I obtained through the Freedom of Information Act. This is the first time the document has been made publicly available. Written by engineers at the Sandia National Laboratories, it gives a reasonably clear explanation of how the various PALs work and includes some photographs of them.

History of PAL (PDF) History of PAL (Text)

“Command and Control Systems for Nuclear Weapons: History and Current Status,” Systems Development Department I, Sandia Laboratories, SLA-73-0415, September, 1973 (SECRET/RESTRICTED DATA/declassified).

Eric Schlosser is the author of “Command and Control.”