Editing Permissive action link (section)

== History ==

=== Background ===
[[File:Sandia-Building800-1951.gif|thumbnail|right|[[Sandia National Laboratories]], 1951. Sandia was instrumental from the beginning in developing PALs.]]

Permissive action links were developed in the United States in a gradual process from the [[Nuclear weapons testing|first use of atomic weapons]] to the early 1960s. In 1953 the [[United States Atomic Energy Commission]] and the [[United States Department of Defense|Department of Defense]] signed the ''Missiles and Rockets Agreement'', which paved the way for the development and implementation of PALs. Certain national laboratories, under the auspices of the AEC, would develop and produce nuclear weapons, while the responsibility for the use and deployment remained with the military. The laboratories were also free to conduct their own research in the field of arms control and security. The thinking behind this was that if the government would ever be interested in such a security device, the research and development of prototypes would already be well advanced. At the beginning of the 1960s, the desire for the usage of such a system grew for both political and technological reasons.

Newer nuclear weapons were less complex in operation, relatively mass-produced (and therefore predictably similar), and less cumbersome to arm and use than previous designs. Accordingly, new methods were necessary to prevent their unauthorized use. As the [[Cold War]] came to a head in the 1960s, the government felt it best not to leave the use of nuclear weapons in the hands of possibly-renegade generals, including the commander of [[Strategic Air Command]] (SAC).<ref>Richard Rhodes: ''Dark Sun: The Making of the Hydrogen Bomb''. Simon & Schuster, New York 1996, {{ISBN|978-0-684-81690-6}}.</ref> Without Permissive Action Links, each nuclear weapon was effectively under the independent control of one person, the general under whose command it happened to fall.

{{quote|I used to worry about the fact that <nowiki>[</nowiki>[[Thomas S. Power|General Power]]<nowiki>]</nowiki> had control over so many weapons and weapon systems and could, under certain conditions, launch the force. Back in the days before we had real positive control [i.e., PAL locks], SAC had the power to do a lot of things, and it was in his hands, and he knew it. |sign=[[Horace M. Wade|General Horace M. Wade]], (at that time subordinate of General Power)|source=<ref>Peter D. Feaver: ''Armed Servants: Agency, Oversight, and Civil-Military Relations''. Harvard University Press, Cambridge 2005, {{ISBN|978-0-674-01761-0}}, S.&nbsp;151.</ref>}}

In order to protect its [[NATO]] allies, the United States had stationed various nuclear weapons overseas; these weapons were thus at least under the partial control of the hosting allied state. This was especially concerning to the [[United States Congress]], as control of these weapons by a third party was in violation of U.S. federal law.{{Citation needed|date=August 2024}} Added to this was the fact that some of the allies were considered potentially unstable—particularly [[West Germany]] and Turkey.<ref name="Assuring Control">Peter Stein, Peter Feaver: ''Assuring Control of Nuclear Weapons: The Evolution of Permissive Action Links''. University Press of America, Lanham 1989, {{ISBN|978-0-8191-6337-0}}.</ref> There was considerable concern that in one of these countries the instructions of the civilian leadership of the host country could overrule that country's military. In addition, the U.S. realized that in the event of war, parts of West Germany would be [[Fulda gap#In the Cold War|overwhelmed early on]], and nuclear weapons stationed there could fall into the hands of the Soviet Union.

For a long time the U.S. military resisted the use of PALs. It feared the loss of its own independence, and it feared malfunction, which could put warheads out of action in a time of crisis. But the advantages of PALs outweighed the disadvantages: thanks to the PALs weapons were able to be distributed to a greater extent in Europe, so as to prevent a rapid and selective destruction or conquest by the Soviet bloc, while still retaining U.S. control over the farther-flung weapons.<ref name="Assuring Control" />

=== Development and dissemination ===
The precursors of permissive action links were simple mechanical [[combination lock]]s that were set into the control systems of nuclear weapons, such as the [[LGM-30 Minuteman|Minuteman]] [[ICBM]]. There they could perform different functions: some blocked the cavity through which the nuclear materials were [[Gun-type fission weapon|shot]] to create a reaction; other locks blocked circuits; and some simply prevented access to the control panel. For testing, some of these mechanisms were installed during 1959 in weapons stationed in Europe.<ref>''Weapon Dispersal without Fear of Unauthorized Use.'' In: ''Sandia Lab News'', Family Day Special Edition, Bd.&nbsp;38 Nr.&nbsp;20, 1986, S.&nbsp;4.</ref>

The work on PAL prototypes remained at low levels until 1960. [[Sandia National Laboratories]] successfully created a number of new combination locks that were adaptable to different types of weapons. In the spring of 1961, there was a series of hearings in Congress, where Sandia presented the prototype of a special electro-mechanical lock, which was then known still as a "proscribed action link".  The military leadership, however, soon realized that this term had negative connotations for the use of weapons by the officer corps ("proscribed" meaning "prohibited"), and decided to start calling PAL "permissive action link" instead ("permissive" meaning "allowing" or "tolerating").{{citation needed|date=August 2017}}

[[File:NSAM 160.jpg|thumb|right| National Security Action Memorandum 160: introduction of PAL to all U.S. nuclear weapons under [[NATO]] command]]

In June 1962, President [[John F. Kennedy]] signed the [[National security directive|National Security Action Memorandum]] number 160. This presidential directive ordered the installation of PALs in all U.S. nuclear weapons in Europe. (U.S. nuclear weapons that were not in Europe were excluded from the order.) The conversion was completed in September 1962 and cost $23 million (${{Formatprice|{{Inflation|US|23000000|1962|r=-6}}}} in {{Inflation-year|US}} dollars{{Inflation-fn|US}}).

According to nuclear safety expert [[Bruce G. Blair]], the US Air Force's [[Strategic Air Command]] worried that in times of need the codes for the Minuteman ICBM force would not be available, so it decided to set the codes to 00000000 in all [[missile launch control center]]s. Blair said the missile launch checklists included an item confirming this combination until 1977.<ref>{{cite web|url=http://www.cdi.org/blair/permissive-action-links.cfm |title=Keeping Presidents in the Nuclear Dark (Episode #1: The Case of the Missing "Permissive Action Links") - Bruce G. Blair, Ph.D |publisher=Cdi.org |date=February 11, 2004 |access-date=April 29, 2010 |url-status=dead |archive-url=https://web.archive.org/web/20120511191600/http://www.cdi.org/blair/permissive-action-links.cfm |archive-date=May 11, 2012 }}</ref> A 2014 article in ''[[Foreign Policy]]'' said that the US Air Force told the [[United States House Committee on Armed Services]] that "A code consisting of eight zeroes has never been used to enable a MM ICBM, as claimed by Dr. Bruce Blair."<ref>{{cite magazine|last1=Lamothe|first1=Dan|title=Air Force Swears: Our Nuke Launch Code Was Never '00000000'|url=https://foreignpolicy.com/2014/01/21/air-force-swears-our-nuke-launch-code-was-never-00000000/|access-date=24 January 2017|magazine=Foreign Policy|date=2014-01-21|archive-date=March 29, 2017|archive-url=https://web.archive.org/web/20170329185801/http://foreignpolicy.com/2014/01/21/air-force-swears-our-nuke-launch-code-was-never-00000000/|url-status=live}}</ref> The Air Force's statement (that 00000000 was never ''used'' to enable an ICBM, i.e. the weapons were not actually launched) does not contradict Blair's statement (that 00000000 was the code for doing so).

The complete conversion to PAL systems was relatively slow. In 1974, U.S. Defense Secretary [[James Schlesinger]] found that a variety of [[tactical nuclear weapons]] were still not fitted with permissive action links, even though the technology had been available for some time.<ref name="Insider">Thomas C. Reed: ''At the Abyss: An Insider’s History of the Cold War.'' Presidio Press, New York 2005, {{ISBN|978-0-89141-837-5}}.</ref> It took another two years until all the tactical nuclear weapons were fully equipped with PALs. In 1981, almost 20 years after the invention of PALs, just over half of U.S. nuclear weapons were still equipped only with mechanical locks.<ref name="Assuring Control"/> It took until 1987 until these were completely replaced.

=== Modernization and the present ===
Over the years the permissive action links have been continuously maintained and upgraded. In 2002, PALs on older [[B61 nuclear bomb]]s were replaced and upgraded with new systems to improve reliability and security, as a part of extending the weapons' service lives to at least 2025.<ref>{{cite web
|author = Grossman, Elaine M.
|url = http://www.nti.org/d_newswire/issues/2008_9_26.html#B8705677
|title = U.S. Air Force Might Modify Nuclear Bomb
|publisher = GlobalSecurity.org
|date = September 26, 2008
|access-date = April 1, 2010
|archive-date = October 9, 2008
|archive-url = https://web.archive.org/web/20081009110808/http://www.nti.org/d_newswire/issues/2008_9_26.html#B8705677
|url-status = live
}}</ref>

'''Code management system'''

The year 1995 saw the development of the code management system (CMS). The CMS has simplified the control and logistics for staff and improved the flexibility and speed in deploying and arming weapons. New codes can be used to recode, lock, and manage the weapons, while the secrecy and validity of the possible launch orders is still ensured. In total, CMS consists of fourteen custom products (nine software and five hardware products).<ref name="Weapons in Europe">Hans M. Kristensen: ''U.S. Nuclear Weapons in Europe''. Natural Resources Defense Council, New York 2005, S.&nbsp;20–21. ([http://www.nrdc.org/nuclear/euro/euro.pdf PDF; 4,9 MB] {{Webarchive|url=https://web.archive.org/web/20140723003003/http://www.nrdc.org/nuclear/euro/euro.pdf |date=July 23, 2014 }}, accessed February 4, 2009).</ref> The software products were developed by Sandia National Laboratories while the hardware was created by the [[National Nuclear Security Administration]].

The CMS was fully operational for the first time in November 2001. A part of the system, a special cryptographic processor fitted into the weapons in 1997 had a potential [[Year 2000 problem]]. By the spring of 2004, all PAL systems were equipped with the CMS. It is thus currently the general foundation for future hardware and software improvements to PALs.