The United States’ Nuclear and Non-Nuclear Weapons Are Dangerously Entangled

New evidence from the Yom Kippur War shows how such knots can lead to nuclear annihilation.

A picture on display shows a Nike missile at one of the facilities that were used to store and potentially launch both conventional and nuclear-tipped Nike missiles in reaction to any Russian attack in Florida on April 8, 2010.
A picture on display shows a Nike missile at one of the facilities that were used to store and potentially launch both conventional and nuclear-tipped Nike missiles in reaction to any Russian attack in Florida on April 8, 2010. Joe Raedle/Getty Images

In October 1973, an unreliable radiation detector could have caused the end of the world. The setting was the Yom Kippur War between Israel and a coalition of Arab states, and the superpowers found themselves being sucked into the conflict. In the war’s febrile final days, the United States detected what appeared to be radiation from a Soviet freighter headed for Egypt and concluded—almost certainly incorrectly—that Moscow was transferring nuclear warheads to Cairo. Partly in response, on Oct. 24, Washington placed its nuclear forces on a global alert for only the fourth time in history—a step it has taken only twice since. The U.S. alert prompted the Soviet Union to reportedly issue a preliminary order to begin the alerting of its own nuclear forces.

This chain of events, which could have culminated in a nuclear war, provides a timely warning. The United States’ ability to detect and track nuclear warheads has improved immeasurably over the last 46 years, making an exact replay of 1973 unlikely. However, growing entanglement between nuclear and nonnuclear weapons is exacerbating closely related dangers. In particular, nuclear-armed states are relying ever more heavily on dual-use weapons, which can accommodate nuclear or nonnuclear warheads, thus exacerbating the risk that one side might wrongly conclude that another had deployed nuclear weapons. In a crisis or conflict, the result could be an escalation spiral that, unlike in 1973, spins all the way to nuclear devastation.

Today, the U.S. nuclear alert of 1973 is usually explained as a warning to Moscow against sending troops to Egypt. That’s unquestionably correct, but it’s only part of the story. In fact, the United States had a second objective, which then-Secretary of Defense James Schlesinger implied when he stated at a press conference on Oct. 26 that the alert was triggered by “other indicators [apart from apparent preparations for troop movements] of military intelligence nature into which I shan’t go.”

These “other indicators” were almost certainly evidence of Soviet nuclear warheads being shipped to Egypt. The suspected shipment was rediscovered by the historian Tim Naftali in 2016 using newly declassified documents, but, in the years after the 1973 alert, it was an integral part of the narrative. For example, it was reported publicly in November 1973—initially on the front page of the New York Times— and discussed by William Quandt, a National Security Council staffer during the crisis, in a 1977 article for International Affairs that describes the run-up to the U.S. alert.

So, the role of the suspected warhead shipment in triggering the 1973 alert isn’t exactly news; what is significant, though, is that compelling evidence that the shipment never took place continues to be overlooked. According to contemporary media reports and later interviews, the United States concluded that the Soviet Union was transferring nuclear warheads to Egypt after detecting radiation from them. Initially, at least, the CIA found this evidence to be persuasive and reported to President Richard Nixon that the ship was “probably” transporting nuclear warheads. It started to walk this conclusion back, however, almost immediately, apparently unnoticed by key decision-makers. By Oct. 30, the CIA could only assess that “there is … at least the possibility that the Soviets have introduced nuclear weapons into the Middle East.” In fact, this assessment contains no unredacted evidence that the ship was actually carrying warheads but does include “strong arguments” to the contrary.

In the months that followed the alert, even stronger evidence against the claimed shipment emerged. Based on interviews, the historian Jeffrey Richelson discovered that the United States had tested the radiation detector involved in the incident and determined that the sensor “was less than completely reliable” and would “often ‘detect’ such radiation when it was not present.”

Not everyone was convinced, of course. In 1983, Gen. George Keegan, who had served as the Air Force’s intelligence chief during the crisis, was still asserting that the shipment had taken place. He claimed that, to interfere with U.S. detectors, the Soviet freighter had created a “magnetic anomaly protection boom.” (No, the authors of this piece have no idea what that is, and one of us has a Ph.D. in physics.)

As tenuous as General Keegan’s pseudoscientific claims were at the time, they now look even further divorced from reality. After the end of the Cold War, the United States discovered troves of previously unknown details about Moscow’s nuclear weapons program. For example, within a month of the Soviet Union’s collapse, former Soviet officials had informed their U.S. counterparts about a previously unknown shipment of nuclear-armed cruise missiles to Cuba in 1962. But in the decades since the 1973 alert, no evidence from the Soviet Union or Russia about a warhead shipment to Egypt has emerged. On the contrary, the one English-language history of the crisis written by a Soviet official notes reports about the “transport of nuclear material” but then explicitly denies that the Politburo even discussed “the deployment … of weapons of mass destruction.”

The detection of nonexistent warheads in 1973 is more than a historical curiosity. In a contemporary crisis or conflict, modern dual-use delivery systems could create a similar danger by leading one protagonist to conclude that an adversary had deployed nuclear weapons when, in fact, it had not.

All nuclear-armed states, apart from the United Kingdom, field such weapons, which include aircraft, cruise missiles, and ballistic missiles. For years, the risks associated with using such weapons have been debated. In the mid-2000s, for example, the U.S. Congress refused to fund a program to replace the nuclear warheads on some Trident D-5 submarine-launched ballistic missiles with conventional weapons out of the concern that Russia might misidentify a conventional missile heading in its direction as a nuclear weapon and launch a precipitous nuclear response.

The 1973 crisis points to another danger that has been largely overlooked: the possibility that non-nuclear weapons might be misidentified as nuclear prior to launch. In this eventuality, a state might misinterpret the readying or moving of conventional weapons by an adversary as nuclear threats or even preparations to use nuclear weapons. It might respond by alerting its own nuclear forces. The result could easily be an escalatory spiral driven by mutual misperception.

The first step to reducing these dangers is to be aware of them. The 1973 alert should help by demonstrating that even imagined nuclear weapons can have potentially existential consequences.

James M. Acton holds the Jessica T. Mathews chair and is the co-director of the Nuclear Policy Program at the Carnegie Endowment for International Peace.

Nick Blanchette is a Ph.D. student in political science at the Massachusetts Institute of Technology.

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