It sounds like decades-old newsreel footage: The president of the United States ordering nuclear-armed B-52 bombers to be given upgraded bases and reportedly kept on constant alert, while the Air Force chief of staff tells a reporter that the military is now pondering, "What does conventional conflict look like with a nuclear element?"

Quotes like that rightfully invoke Soviet-U.S. tensions in the age of Eisenhower—a time warp that's enhanced by the current use of B-52s, which were new in 1955. But the focus on the Korean peninsula is actually more reminiscent of 1969. Back then, President Richard Nixon and key aides like Henry Kissinger faced a crisis in North Korea that any subsequent administration could recognize.

In April 1969 a North Korean fighter shot down a U.S. Navy reconnaissance plane, killing 31 and prompting Nixon's team to draw up plans to respond. Those plans, according to documents declassified 47 years later, included nuking large swatches of the communist nation.

"What does conventional conflict look like with a nuclear element?"

Of course, the United States did not pull the trigger. At the end of the day, Nixon found what every president has encountered: Solutions in North Korea are all or nothing. The rouge nation is too threatening to target with small military measures, while actually effective strategies would rely on massive military attacks using weapons of mass destruction. Kissinger called this dilemma "the extreme end of possibilities."

Today we can learn some grim lessons about what has changed in Asia (and what hasn't) by comparing what we know about Nixon's plans with the current situation. Every president has come to this moment with North Korea, and now that it's his turn, Trump has moved nuclear assets around the global chessboard. Maybe it's a display of brinksmanship. Maybe he really is preparing for action. In any case, many people are understandably fretting over his actually using them. Fewer are asking why and how the Pentagon would employ them. That's where the Nixon memo comes in, as a springboard of this unsettling conversation.

Radioactive Freedom Drop

U.S. Air Force/Tech. Sgt. Robert J. Horstman

Nixon's plan to nuke North Korea was called Operation Freedom Drop. The memo that conceived it—"Nuclear Contingency Plan for North Korea"—had the stated purpose "to provide pre-coordinated options for the selective use of tactical nuclear weapons North Korea."

Now, the jargon gets obtuse and controversial here, but for the purpose on this discussion, any nuclear attack that doesn't involved reducing entire cities to ash is "tactical." In 1969, and in 2017, the Pentagon's goal is and was not to exterminate North Korean cities and resettle the land a couple hundred years from later. Rather, the plan was to use small-yield nukes to de-fang the dangerous North Korean military.

The Nixon memos show that the Pentagon didn't see an easy way to destroy the North Korean air force without resorting to a wider war over the entire peninsula. There were too many airbases to strike and not enough U.S. planes to fly over them without risking an extended campaign and high casualties.

Kissinger called this dilemma "the extreme end of possibilities."

These days, the tech is much different but the challenge remains the same. In 1969, as now, air power is the first solution for American military planners. But in both cases the sheer weight of threats works against American bombers. The North Korean air force is no trouble anymore, but advanced anti-aircraft weaponry pose real risk to pilots.

The risk of retaliation for U.S. air strikes is alarmingly real. These days the northern regime could load its artillery with chemical and biological weapons. They have nuclear weapons of their own—short-range blackmail weapons mounted on ballistic rockets that can reach places like Japan and the U.S. airbase in Guam, not to mention South Korea.

This regime still has a military arsenal that is too ferocious to simply wound. It has to be broken, quickly and with little room for mistakes.A massive conventional response may not be enough to prevent bloody retaliation. A hypothetical massive barrage of cruise missiles, stealth warplanes, and Special Forces missions couldn't knock out the entire North Korean command and control network, nuclear sites, air defenses, naval bases and military airports. The regime has buried much of its critical weapons underground, including mobile ballistic missile launchers. The retaliation of a wounded North Korea could kill hundreds of thousands, or more.

One-shot operations with slim margins of error require a weapon so devastating that one bomb can eradicate an entire airbase. Maybe this is a job for nukes. That's what the Pentagon pondered in 1969. It's thinking consider the same thing now. "Would not a quick and ferocious response that would clearly be a 'one shot' operation be a more suitable course in order to discourage North Korea from further response?" Kissinger asks in the declassified documents.

The Nuclear Option

North Korean leader Kim Jong un with model of a nuclear device. AFP PHOTO/KCNA VIA KNS

The Pentagon offered as many as 13 solutions in the 1969 memo, including the infamous Tab L contingency called Freedom Drop. This option has three choices, ranging from amazingly destructive to devastating.

One option proposed pasting all 16 major North Korean airbases "with nuclear weapons with a yield of 70 kilotons each to neutralize the North Korean air order of battle in response to a North Korean air attack on South Korea." Another plan used a range of nuclear yields against a wider target set to gut the regime's ability to make war with ground, naval, or air units.

But the remaining choice, the first option offered in the classified memo, is the most relevant to 2017. This plan would rely on nuclear weapons with yields that most closely resemble the ones that Trump is putting on alert status. Option 1 called for nuclear attacks on North Korean command centers, airfields, and naval bases with atomic weapons ranging from .2 to 10 kilotons.

A one-kiloton nuke at ground level is enough to create a 500 foot-wide fireball and 3rd degree burns at a half mile. The deadly radiation band would be a mile wide, about the distance from the White House to the Washington Monument. (For some scale, the Minuteman III today carries at least one W87 warhead of 475 kilotons or a W78 packing 350 kilotons.)

Just as was the case in Nixon's day, the use of small yield nuclear weapons in 2017 is attractive to planners because they are guaranteed to destroy what they're aimed at. In a conflict where there are not enough warheads available to hit every target, the appeal of a single missile that can close an airbase a potent one. In the current crisis, strike planners must think of ways to disable targets that are buried in tunnels and dug into mountains. A small nuke could be used to annihilate the entrance with a low-yield nuclear weapon.

The risk, as always, is that the use of even small nukes against a nation that has its own nuclear weapons is a good way to start a wider nuclear war. Nukes are an elegant solution for a vexing problem—if you don't mind risking a wider nuclear war and an estimated 8 million civilian casualties.

Carter's Cruisers

A B-1B Lancer from the U.S. Air Force 28th Air Expeditionary Wing heads out on a combat mission in support of strikes on Afghanistan in this image released December 7, 2001. Getty Images

Let's say Trump wanted to launch some small nuclear missiles that could detonate at the mouth of an underground military base and render the site useless. To do this, he'd want nuclear-tipped cruise missiles. And here, once again, presidential history comes into play.

In 1977 President Jimmy Carter decided the U.S. didn't need the supersonic bomber that the Air Force had been building since 1969. At that time, Nixon didn't like the range of air power options to deal with problems like North Korea, so he ordered a new bomber. It would be called the B-1, and it could do things the B-52 couldn't, like fly fast and low to drop nukes on enemies and escape to do it again later.

As happens with weapons programs, new technology rendered the last version less appealing. By 1977 the B-2 stealth bomber prototypes and improving cruise missiles were making bombers seem obsolete, so Carter cancelled the B-1 program. (Ronald Reagan would restart it, and the B-1 Lancer still flies today, now armed with only conventional weapons.)

Without B-1s on the way, the B-52s needed to stay dangerous in a new environment. They needed new weapons that could keep the big planes away from improving surface-to-air missiles. The solution became nuclear-tipped cruise missiles that could drop from the bomb bay, flare to life and zip to targets at low altitudes, where radar has a harder time spotting them. Who needed new bombers when you have air-launched cruise missiles that can deliver the nuclear warheads from a safe distance?

As years went by, the power of radar-evading stealth airplanes turned that dynamic on its head. And the small nuclear yield of modern cruise missiles seemed more like a dangerous temptation than a deterrent. A small nuke is easier to use than a big one, but it's still a nuke. Yet even as the resurrected B-1 took flight and the B-2 changed the deterrence game, the nuclear tipped cruise missile remained in the U.S. inventory.

It took a while, but the B-52s have fully graduated from bomb drops to standoff nuclear delivery. This May, the Federation of American Scientists noticed that the B-52 doesn't even carry nuclear gravity bombs anymore. Instead, a B-52 carries as many as 20 nuclear-tipped cruise missiles that can be launched from nearly 1,500 miles away. The missiles drop to hug the terrain, programmed to fly whatever route avoids anti-aircraft battery along the way, staying out of range of some defenses and using mountains and valleys to foul shots.

When Donald Trump reportedly ordered the B-52s on constant alert this past weekend, he put into the North Korean mind this specter of an unexpected nuclear strike. As these small nukes would fly deeper in North Korea, the South Korean and American naval and air forces could focus on destroying artillery and units along the border and closer to population centers. Keeping any sized nuclear attack away from the borders of South Korea and China would obviously be a wise choice.

Whether the world's first attempt at "limited nuclear war" remains limited depends on the effectiveness of the cruise missiles and, even more so, intelligence gathering. It wouldn't take many hidden mobile ballistic launchers to survive the first strike for wreak havoc major Asian cities.

So the North Korea nuke game is all or nothing. The conventional wisdom has been that the U.S. and its allies in the area need to launch a massive attack, with all of its risks, or no attack at all. The words of presidents Trump and Japanese president Abe have been strident, but the words are backed by movements of military hardware. So the question remains: Will Trump make the ultimate gamble and make the use of small nuclear weapons part of a response, or even a first strike? And how many lives are at stake, depending on the answer?

Joe Pappalardo is a frequent contributor to Popular Mechanics and the editor-in-chief of the Dallas Observer. His new book, , releases on November 21, 2017, and you can .

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