The first sign of a 21st Century nuclear war might be command post sensors lighting up and aircraft radios buzzing as pilots notice a strange-looking cloud forming. Heat rises as ground troops a few dozen miles away feel the winds shift.

Satellite communications are out. So are some ground links.

U.S. and allied command posts can’t reach brigades in the field.

Forward deployed troops would see the intelligence finally come streaming in, followed by orders from the Combatant Command — strike back, use our tactical nukes if you must. And by the way, some unlucky troops will need to roll into that area to assess the damage, counterattack and aid any survivors.

The world has not seen a nuclear strike in combat since 1945. But a nuclear attack from an enemy — and potential U.S. counter strike — is a scenario that’s drawing renewed attention from the Defense Department as the military prepares for the grim prospect of full-scale combat operations involving nuclear weapons.

“It’d be horrible,” retired Gen. Hawk Carlisle, former head of Air Combat Command and current head of the National Defense Industrial Association, said of this hypothetical scenario that could happen under new Pentagon doctrine.

“All the complicating factors of a nuclear exchange just accentuates whatever problem you would have in a normal hostile environment, with a level of complexity that is an order of magnitude more difficult,” Carlisle told Military Times in a recent interview.

For the first time in decades, incorporating tactical-level targeting and being able to run maneuver operations in a post-nuclear blast area have returned to the thinking of even the lowest-ranking troops. Something most operational planners have ignored for decades.

Winning a nuclear ground war

The Pentagon’s new plans were outlined in detail when the Pentagon recently published its new 60-page “Joint ­Publication No. 3-72 Nuclear Operations” online. The ­document, prepared at the request of the Chairman of the Joint Chiefs of Staff, was briefly available to the public but soon removed and placed in an online catalogue of “for official use only” documents.

The document reveals a fundamental change from the Cold War-era belief that nuclear war would result in an Armageddon-like catastrophe and “mutually assured destruction.”

The new plans reflect the modern battlefield where the number of countries with nuclear capabilities is growing rapidly, where asymmetric warfare is increasingly common and where the U.S. military is losing its technological edge over other near-peer military rivals.

The new plan bluntly states that “nuclear weapons could create conditions for decisive results and the restoration of strategic stability. Specifically, the use of nuclear weapons will fundamentally change the scope of a battle and develop situations that call for commanders to win.”

And it calls their use “essential” to mission success.

Collectively, it amounts to a new “prevail in conflict” or fight to win doctrine, said Steve Aftergood, a national security analyst at the Federation of American Scientists. The Defense Department’s latest nuclear plan may be a reaction to the Russian strategy of using nuclear weapons in an effort to “escalate to deescalate,” Aftergood said.

Russia’s nuclear policy since 2000 has been to use smaller payloads in a conventional fight — low-yield or tactical — nuclear weapons to win key battles that could quickly end conflict and prevent full-scale nuclear war, according to a 2012 U.S. National Intelligence Council report.

Some experts see the doctrinal change as simply a way of getting back to the way nuclear conflict was viewed before the Berlin Wall fell.

Before the Berlin Wall fell and the collapse of the Soviet Union in 1991, every U.S. artillery unit in Europe was nuclear capable. “Every battalion had nuclear training,” said David E. Johnson, principal researcher at the Rand Corporation and career Army officer with a background in artillery.

That included defending nuclear weapon storage sites, anticipating effects of even howitzer 155 mm nuclear-enabled projectiles and working field exercises in mission oriented protective posture, or MOPP, gear.

“We need to recover that capability,” he said. “There’s just a knowledge gap in the force.”

Post-blast ground operations

The 2019 nuclear doctrine calls for soldiers and Marines trained and prepared to conduct combat operations in a multitheater post-nuclear environment.

“The greatest and least understood challenge ­confronting troops in a nuclear conflict is how to operate in a post-nuclear detonation radiological environment,” the publication states.

And it highlights the special physical and ­physiological hazards, and psychological effects of the nuclear ­battlefield, but notes that training and guidance are ­required for troops to accomplish their mission.

“Commanders should know how nuclear weapon effects can affect personnel, equipment, and the dynamics of ­combat power. They should train for and implement survivability measures and techniques,” according to the doctrine.

The dynamics of a post-nuclear blast environment have changed since the Cold War as the U.S. military — and its adversaries — are increasingly dependent on complex ­communications systems.

A nuclear weapon unleashes an electromagnetic pulse, or EMP, that could completely disable electronic equipment, crippling communications and platforms, said Bryan Clark, senior fellow at the Center for Strategic and Budgetary Assessments, former nuclear submariner and previous special assistant to the Chief of Naval Operations.

A nuclear blast detonated in the upper atmosphere would take out low-orbit satellites, which bigger U.S. military systems rely on to communicate across regions and theaters, he said. U.S. commanders or enemy forces could carefully calibrate both the yield of the weapon as well as the height of the blast in a way to specifically target communications systems rather than massive military or civilian casualties.

“The EMP effect is not the side effect,” Clark said. “In a lot of cases it’s the primary effect. It gets you massive catastrophic effect on electronics without casualties or infrastructure damage.”

But, Carlisle said, though some capabilities would get knocked out, the services could still operate.

“Would there be degradation? Yes. Would we try to find a way to mitigate it and work around it? Yes. It’s all of those things,” he said.

Targeting options

The plan calls for geographic ­combatant commanders to provide guidance to the president regarding choices of nuclear weapons targets and the resulting mitigation of damage.

The commanders can nominate targets for nuclear options that would support their ongoing operations, according to the publication.

The doctrine calls for field ­commanders below the combatant commanders to make recommendations while intelligence selects targets, they work as a team, the objectives are then given to STRATCOM, which creates a target list of military objectives for the president.

“In other words, commanders in the field would not only execute orders from the national command ­authority, but they would also participate in battle planning. This tends to normalize the possibility of nuclear war fighting,” Aftergood said.

When targeting, the doctrine advises commanders they must consider the yield of the weapon, the height of burst, fallout, what weapon system will deploy the armament and the law of war governing what they can strike and when.

Preparing the force

Air Force, Marine Corps and Army spokespersons told Military Times that the joint doctrine change has not caused any expansion in their nuclear response mission or training.

The smallest branch, the Marines, for example has an estimated

1,634 personnel whose part or all of their job training is specific to chemical, biological, radiological or nuclear tasks. The Army Guard and Reserve forces also contain entire units dedicated to CBRN response in the homeland and support theater operations in major combat.

The Nuclear Operations publication update as a “desire to prepare conventional forces to operate in a nuclear environment,” said Ian Williams, deputy director of the Missile Defense Project at the Center for Strategic And International Studies and a former Army engineer.

“It’s a reaction to the realities that we’re seeing, the kinds of threats and ­adversaries the Pentagon is turning its attention to,” Williams said.

Michaela Dodge, a missile defense and nuclear deterrence expert with the Heritage Foundation said the ­geographic combatant commanders have to be aware that with Russian, Chinese and North Korean doctrine, planning for their use of nukes is a reality.

The document seems to be telling commanders to think about and plan how operations will be impacted should an opponent use nuclear ­weapons, she said.

In an article titled, “U.S. Army Doctrine Dislocated with Nuclear-Armed Adversaries and Limited War” in the January-February issue of the journal Military Review, Army Maj. Zachary L. Morris criticizes the Army’s most recent Field Manual 3-0 Operations, which covers large-scale combat but neglects to address how enemies with nuclear weapons will be handled.

“If the United States seeks a decisive victory, often by altering an adversary’s government, there would be little reason for an adversary to avoid using nuclear weapons,” Morris wrote.

Morris points to Russia ending its 2009 annual exercise with a simulated nuclear strike on Warsaw, Poland. And in October 2016, Russia conducted a massive exercise evacuating government from Moscow after a simulated nuclear attack on the homeland.

He claims conventional strikes on fire and command and control systems in China or North Korea would incentivize those states to use nuclear weapons.

“[T]hese are considered a precursor to disarming a first strike or enabling a decisive victory — increasing a ‘use it or lose it’ mentality in the target state,” he wrote.

The 2019 nuclear doctrine may be the most recent change to joint doctrine, but the Army and Marines also have recently updated operational and tactical training requirements for nuclear protection and operations-related work.

A February Marine Corps Order laid out how chemical, biological, ­radiological and nuclear teams would be assigned for training and missions at the major subordinate commands and down to the battalion and squad level.

A 2017 Army manual, titled “­Combined Arms Countering Weapons of Mass Destruction,” provides guidance on how to plan targeting weapons of mass destruction facilities and teaming ground combat units with CBRN teams to detect such hazards.

Like the Nuclear Operations doctrine, the same manual also advises commanders to have both prioritized and predetermined targets but be ready to work on the fly during major combat operations.

In March 2017, the Marine Corps ­introduced a “CBRN readiness ­calculator” in an administrative message that directs unit commanders to use for assessing their unit’s ability to perform its mission under CBRN conditions.

The message noted that “several inconsistencies have been observed in the reporting of CBRN readiness across the Marine Corps.” The calculator is an attempt to provide a uniform way to gauge readiness.

All of these moves indicate a ­reprioritizing of nuclear preparations — both defensive and offensive.

Tactical Nuclear Weapons

When asked for comment, STRATCOM directed Military Times to Commanding General John E. Hyten’s statement before the House Armed Services Committee on May 2019.

New low-yield nuclear weapons and their funding was the centerpiece of STRATCOM’s testimony and cited the likely existence of low-yield weapons already in place in China, Russia and North Korea.

Hyten said he preferred submarines, rather than aircraft, be the delivery system for low-yield weapons. Because while low-yield payloads can be delivered by air, it is more challenging due to the difficulty of aircraft having to fight through a denied environment.

Those strikes could come from a variety of platforms, but the doctrine ­highlights the flexibility of using ­long-range bombers and dual-capable fighter aircraft for their mobility.

Tactical nuclear weapons include ­gravity bombs, short-range missiles, artillery shells, land mines, depth charges and torpedoes which are equipped with nuclear warheads, nuclear armed ground-based or shipborne surface-to-air missiles and air-to-air missiles. Tactical nuclear weapons have specific features meant to enhance their battlefield characteristics, such as variable yield which allow their explosive power to be varied over a wide range for different situations.

Out at sea or in the skies

While ground troops would have the most immediate problems, the sea and air services face a host of their own concerns.

For sailors that means installing special air filters on ships and having replacements for extended ops. Also, they’ll have to button up the surface, which will need to be decontaminated by crews of specially trained sailors in protective suits.

Depending on the level of contamination, some ships might have to be pulled from the fight and even disassembled for cleaning, Clark said.

Flying airplanes and helicopters in a post-nuclear detonation environment — for combat and other missions — means dealing with radioactive fallout, tracking intensity and drift, Carlisle said.

The Air Force took cues from how the Navy protects sailors who work on nuclear-powered submarines and aircraft carriers and built procedures to quarantine aircraft that had flown through radioactive clouds.

The Air Force’s experience helping Japan in the immediate aftermath of the 2011 Fukushima Dai-Ichi Nuclear Plant meltdown could show how it might operate under those conditions, Carlisle said.

As part of Operation ­Tomodachi the Air Force flew a variety of aircraft for weeks, conducting ­search-and-rescue, reconnaissance, and cargo delivery missions in the broader ­tsunami-devastated area.

But when those potentially ­contaminated aircraft returned to ­bases such as Kadena and Yokota, there was a problem.

“You don’t taxi that airplane into a ramp alongside all the other ­airplanes,” Carlisle said. “So, you had to do management of the airfield to figure out where you’re going to put the airplanes that need to be ­decontaminated, and how you go about decontaminating them.”

Bases cordoned off a few areas ­specifically for cleaning and maintenance of those aircraft, he said. Only people with the right training, ­equipment and coverings could go near them and air flow and wind direction had to be monitored.

Air Force “nuclear sniffers,” which search the atmosphere for signs of nuclear explosions — as well as other unmanned aircraft — would likely be crucial to managing a nuclear battlefield, Carlisle said.

While sniffers detect the location and fallout levels, he said, ­weather airmen analyze wind and other ­meteorological patterns to track and predict how the radiation might drift and dissipate.

Despite decades of practice in the past, from ships to planes to individual troops, the Pentagon has to figure out how to fight in one of the most deadly environments ever envisioned.

“We have been working on it for a few years, and we do have more ­information than we probably had in the height of Iraqi Freedom and Enduring Freedom," Carlisle said.

“We don’t have anywhere close to all the answers … and not to the level of detail … we need,” he said. “But we are trying to figure it out.