As D-Day drew near, Gen. George C. Marshall, the Army chief of staff, dispatched a messenger to Gen. Dwight D. Eisenhower in London. Eisenhower was instructed to meet alone with the messenger, a mere major. Part of the secret Operation Peppermint, he was a specialist in radiological poisons.

Washington worried that Germany might use, as a defensive weapon, radioactive residues from small nuclear reactions to contaminate large areas, such as Normandy’s beaches. Neither seen nor smelled, the residues could disable, even kill, troops.

This threat did not materialize; neither did another, the military use of cholera. But human rights lawyer Michel Paradis shows, in his new book “The Light of Battle,” that Eisenhower took these threats seriously. They were markedly less menacing than what Roger Brent (professor of basic sciences), T. Greg McKelvey Jr. (adviser to the Rand think tank) and Jason Matheny (Rand’s chief executive) describe in their Foreign Affairs article “The New Bioweapons.”

The coronavirus, they write, was “an unthinking adversary” that probed the world’s defenses against new pathogens. Considering the toll the pandemic took in lives and social disorganization, imagine the “remarkably deadly” pathogens that thinking adversaries might design using rapidly advancing knowledge of molecular and human biology: “In a worst-case scenario, the worldwide death toll might exceed that of the Black Death” in the 14th century that killed 1 in 3 Europeans.

In World War I, Germany used pathogens to attack horses and mules the Allies were using for transportation. In World War II, in occupied Manchuria, Japan’s Unit 731 tested biological weapons on humans. When defeat approached, a Japanese officer proposed operation Cherry Blossoms at Night: seaplanes dispersing bubonic-plague-infected fleas over U.S. West Coast cities.

In the 1960s, the authors say, the U.S. Defense Department Project 112 trained for the mass distribution of offensive pathogens (practicing with spores in New York subway tunnels, bacteria in aerosols from boats in San Francisco Bay, chemicals sprayed by planes from the Rockies to the Atlantic) in case a Soviet first strike neutralized the U.S. nuclear arsenal.

By that decade’s end, the government had “sizable quantities of deadly bacteria and toxins” that could be as deadly as nuclear weapons but were easier to construct. The biological weapons were, according to a microbiologist, designed to “confound diagnosis and frustrate treatment.”

In 1972, the Soviet Union signed the Biological Weapons Convention — a ban. The Soviet biological weapons program existed until the country fell apart, and reportedly employed 60,000 at its height.

Time was, the authors note, biology seemed “a force for progress,” as with the elimination of smallpox and the near-eradication of polio, and HIV no longer kills almost everyone infected. But, the authors stress, progress in biology “can be a double-edged sword.” As poet Ogden Nash (1902-1971) said, “Progress may have been all right once, but it went on too long.”

In this century, the arrival of the CRISPR-Cas9 gene-editing system heralded great leaps forward in molecular biological engineering, for better (e.g., a gene therapy for sickle cell anemia) or worse. Brent, McKelvey and Matheny warn that for would-be terrorists, biological engineering, vastly accelerated by artificial intelligence, “could ease the path to mayhem”:

“If bad actors do eventually produce and release a viral pathogen, it could infect vast swaths of the human population in far less time than it would take officials to detect and identify the threat and start fighting back. Generating pathogens, after all, is cheaper than defending against them. The U.S. State Department assessed that North Korea and Russia have offensive biological weapons programs and that China and Iran are pursuing biological activities that could be weaponized.”

In 1969, Joshua Lederberg, a Nobel Prize-winning biologist, warned that the proliferation of biological weapons would be like making “hydrogen bombs available at the supermarket.” Biological weapons confound the Cold War paradigm of deterrence because those releasing them can evade detection and hence retaliation.

Brent, McKelvey and Matheny urge “hardening” societies: developing “warning systems” to detect engineered diseases. (The coronavirus might have been one.) And preparing to surge production of personal protective equipment, vaccines and antiviral drugs. The world must “develop the ability to vaccinate its eight billion people within 100 days of an outbreak — faster than it took the United States to fully vaccinate 100 million people against Covid-19.”

John von Neumann — mathematician, physicist and participant in the Manhattan Project — said: “For progress, there is no cure.” There is only politics in the service of prudence. Remember this as you listen, so far in vain, for evidence, from either candidate to be the next commander in chief, of seriousness concerning national security.

George Will writes a column for the Washington Post. His email address is georgewill@washpost.com.