KARACHI, Pakistan — The Karachi Naval Dockyard, home port and strategic nerve center for Pakistan’s fleet, sits on a sliver of land bracketed between Port Grand, a “family fun” pier that features kiddie rides and a panoramic view of warships at anchor, and Machar Colony, a sprawling slum where cattle graze on garbage and a million human inhabitants live in nearly unimaginable squalor.

It was here, during the quiet predawn of May 6, 2014, that four rogue naval officers walked up the gangway of the PNS Zulfiqar, a 4,000-ton frigate that was preparing to put to sea. A guard inspected their ID badges and saluted. Once on board, their plan was to join up with another group of six militants disguised in marine uniforms who were approaching the Zulfiqar in an inflatable dinghy. Together they hoped to hijack the ship and use it to attack a US Navy patrol in the Indian Ocean.

But an alert sailor on board the frigate noticed something was wrong. The men in the dinghy were armed with AK-47s — not the standard weapons used by Pakistani marines. When he challenged the group in the dinghy, a gunfight quickly erupted. While the attackers fired automatic weapons and rocket-propelled grenades, the sailor shredded the dingy with an anti-aircraft gun, killing all six.

Hearing the commotion, navy commandos from another vessel rushed to the scene, but it still took several hours to regain control of the ship from the four rogue officers already on board. Eventually all of them were killed, the last one blowing himself up after he was cornered.

The audacity of a bloody attack inside one of the most heavily secured naval facilities in Pakistan was jarring enough. Even more jarring was the source of the attack: al-Qaeda, which claimed responsibility for the strike and praised the dead men as “martyrs.” Five more naval officers implicated in the plot were later arrested, charged with mutiny, and sentenced to death.

The Zulfiqar incident is the most serious in a long string of deadly security breaches at Pakistani military installations, including attacks on nuclear facilities near Dera Ghazi Khan in 2003 and 2006 and a string of attacks on the air force bases at Sargodha and Kamra between 2007 and 2012 (the strikes were detailed in research by Ankit Panda and Christopher Clary, two leading scholars on the nuclear arms race between India and Pakistan). One of the most horrifying strikes was a gruesome 2014 attack on a school for the children of military officers in Peshawar that left more than 140 people dead, including 132 children.

But even if Pakistani bases have been hit before, the Zulfiqar strike is particularly alarming. That’s because Pakistan is preparing to arm its submarines and possibly some of its surface ships with nuclear weapons — which means terrorists who successfully fight their way into a Pakistani naval base in the future could potentially get their hands on some of the most dangerous weapons on earth.

The Pakistan navy is likely to soon place nuclear-tipped cruise missiles on up to three of its five French-built diesel-electric submarines. It has also reached a deal with China to buy eight more diesel-electric attack submarines that can be equipped with nuclear weapons. These are scheduled for delivery in 2028. Even more disturbing, Pakistani military authorities say they are considering the possibility of putting nuclear-tipped cruise missiles on surface vessels like the Zulfiqar.

The new generation of nuclear submarines increases the risk of a devastating war between India and Pakistan

Pakistan says its decision to add nuclear weapons to its navy is a direct response to India’s August 2016 deployment of its first nuclear submarine, the Arihant. A second, even more advanced Indian nuclear submarine, the Arighat, began sea trials last November, and four more boats are scheduled to join the fleet by 2025. That will give India a complete “nuclear triad,” which means the country will have the ability to deliver a nuclear strike by land-based missiles, by warplanes, and by submarines.

The submarine is the key component. It’s considered the most “survivable” in the event of a devastating first strike by an enemy, and thus able to deliver a retaliatory second strike. In the theology of nuclear deterrence, the point of this unholy trinity is to make nuclear war unwinnable and, therefore, pointless.

When it comes to India and Pakistan, by contrast, the new generation of nuclear submarines could increase the risk of a devastating war between the two longstanding enemies, not make it less likely.

India and Pakistan have gone to war four times since 1947, when Britain partitioned what had been a single colony into Hindu-majority India and Muslim-majority Pakistan. They have been in a state of constant hostility ever since, and for the past two decades, they have been locked in a frightening nuclear arms race on land. Pushing the contest into the Indian Ocean makes the situation even more dangerous by loosening the chain of command and control over the weapons, increasing the number of weapons, and placing them in an environment where things tend to go wrong.

“The nuclearization of the Indian Ocean has begun,” Zafar Jaspal, a nuclear security expert at Islamabad’s Quaid-i-Azam University, told me. “Both states have now crossed the threshold.”

This should be setting off alarms throughout the international community. Growing numbers of nuclear weapons will soon be deployed to submarines patrolling some of the most bitterly contested waters on earth — and controlled by jittery and potentially paranoid officers on perpetual high alert about a surprise attack from the other side.

The result is a game of nuclear chicken every bit as dangerous as the “my button is bigger than yours” competition between Donald Trump and Kim Jong Un on the Korean Peninsula. The difference here is that this one is going almost completely unnoticed.

Putting nukes on submarines makes a nuclear war much more likely

The modern nuclear-powered, nuclear-armed submarine is arguably the most fearsome weapon ever conceived. The US Navy has 18 Ohio-class boats, four of which can carry 154 cruise missiles apiece. The submarines can travel beneath the sea for months, virtually undetectable, and their range is limited only by the crew’s endurance and food supply.

When we talk about nuclear submarines, we talk about two different, but related, things: what powers the subs, and what kinds of weapons they carry. The US, Russia, the UK, France, and China have nuclear-powered submarines that are also armed with nuclear weapons. Israel is thought to have submarines that are armed with nuclear warheads, but they’re powered by diesel-electric generators. That matters because those types of submarines, unlike the nuclear-powered ones made by America and other major world powers, are noisy — and thus easier to track — and can generally stay underwater for only a week or two at most.

India has spent billions of dollars to join that exclusive club — and came close to disaster. The $2.9 billion Arihant nearly sank a few months after its commissioning when a hatch was left open and seawater flooded the propulsion compartment. The embarrassing mishap, blamed on “human error,” was hushed up by the ministry of defense. Even India’s senior political leadership was kept in the dark. The boat has been undergoing extensive repairs since February 2017, according to a January 8 report in the newspaper the Hindu, which was the first to report the entire saga.

Meanwhile, India’s “other” nuclear submarine, the INS Chaka — an Akula-class submarine on loan from Russia primarily for training purposes — is also in dry dock after an unspecified accident damaged its sensitive sonar equipment. In February, Russia sent India a $20 million bill for repairs.

Pakistan, for its part, announced last year that it had successfully test-fired a submarine-launched cruise missile capable of carrying a nuclear warhead. That was a clear indication that the country wanted to start arming its submarines with nukes. It had already signaled that it was willing to put nukes on some of its surface ships.

The problem is that putting nukes at sea significantly weakens the chain of command and control over the weapons, which means the risk of an accidental exchange of fire — or full-on nuclear war — between India and Pakistan will increase exponentially.

Up until now, both Pakistan and India have implemented rigorous checks to keep their weapons safe and eliminate the possibility of inadvertent or rogue launches. In India, ultimate authority in the chain of command and control rests with the country’s civilian political leadership.

In theory, Pakistan’s nuclear trigger is also in civilian hands. A body called the National Command Authority, headed by the prime minister, must authorize any decision to use nuclear weapons. But in reality, it is the military, widely regarded as the most stable and disciplined institution in the country, that controls all aspects of the country’s nuclear program.

Equally important, both India and Pakistan have kept their warheads and delivery systems “de-mated” — that is, the nuclear warhead is stored far away from the missile that would deliver it. Or in the case of India’s bombs, the trigger or detonator is kept far from the fissile core.

But at sea — and especially when you go beneath the sea — this is pretty much impossible. The warheads and missiles have already been assembled and stored in the same place, and individual submarine captains have significant freedom to decide whether to launch their nukes.

“The new danger for both countries is that the problem of command and control over the submarines becomes very tenuous,” said Pervez Hoodbhoy, a Pakistani nuclear physicist and frequent visiting scholar at Princeton University, where we spoke last summer. “With land-based weapons, the warhead is separated from the delivery system. You can’t do that with warheads on a submarine. When it leaves the port, it is already armed.”

Hoodbhoy said that leaves military planners with two options: “Either you do not give the arming code to the captain … or you give it to him before he leaves the port and he can, of his own accord, launch a nuclear missile.”

In submarine warfare, the glaring weak link in the chain of command has always been communication between the sub beneath the sea and the central command. Normal radio waves cannot penetrate the ocean’s depths. To communicate with a submerged submarine, very low frequency (VLF) and extremely low frequency (ELF) radio transmissions are necessary. These frequencies cannot carry voice communications, only coded messages or — at a snail’s pace — text messages. It’s also difficult for the subs to receive communications of any kind if they’re submerged too deeply.

These communications are also strictly one-way; subs can hear what ground commanders are telling them but can’t reply or ask questions. “Essentially the submarine is on its own,” said Hoodbhoy, adding that “it can’t communicate back” unless it sticks an antenna above the surface and potentially reveals its location.

Hiding beneath the ocean, almost impossible to detect, nuclear submarines have the great advantage of being able to survive a nuclear strike by an enemy nation and launch a devastating second-strike response. The same can’t be said for the land-based VLF transmitters that give the subs their orders. These are impossible-to-hide sitting ducks, vulnerable to enemy attack in a first strike. Knock out these installations and the submarines are operating blind.

If you watch Denzel Washington and Gene Hackman fight it out in the underwater thriller Crimson Tide, you get a pretty accurate picture of how things can go south quickly in the extreme isolation of a nuclear submarine cut off from its centralized command.

Pakistan and India went to the nuclear brink during a 1999 war in the disputed territory Kashmir, coming closer to pulling the trigger than even the US and Soviet Union during the 1962 Cuban missile crisis. The Kashmir issue continues to roil both countries, so it’s not hard to imagine a Crimson Tide scenario in which an Indian submarine commander, aware that his country is under attack, receives an incomplete or unclear order to launch. What does he do?

Here’s another scenario: India knocks out Pakistan’s only VLF transmitter in Karachi. The beleaguered commander of one of Pakistan’s diesel-electric submarines — lost in the fog of war, unable to communicate with the National Command Authority, and under attack by one of India’s highly capable anti-submarine hunters — launches a cruise missile. Is it armed with a conventional warhead or a nuclear warhead? Do Indian authorities wait until it hits a major population center to find out? Or do they order an immediate retaliatory attack?

Experts who have modeled an India-Pakistan nuclear exchange say that once the first nuke is launched, it would be nearly impossible for either side to deescalate.

That means each side would likely attempt to unleash its entire arsenal of 100 or more nuclear weapons on the other side’s population centers. The ensuing firestorm would release a cloud of radioactive ash that would darken skies, cool temperatures, and disrupt agriculture around the globe for a decade or more. Millions would die, and millions more would be faced with displacement and starvation as we enter what scientists have termed nuclear winter.

In many ways, the power to start — or prevent — such devastation rests in the hands of individual submarine commanders. During the Cold War, US submarines had a “two-man rule” that required a commander (Hackman’s character in Crimson Tide) and executive officer (the part played by Washington) to agree that a launch order was valid.

As Cold War tensions eased, the two-man rule was replaced by a more rigorous system of checks that require the sub commander to utilize an externally provided code in order to launch.

India has not said how it will maintain control of its submarines. “There’s a lot of confusion and not much clarity on this,” said Yogesh Joshi, an analyst at Stanford University who is writing a book on India’s nuclear submarine program. “They are acting as if this is something still in the future, something they can think about later.”

The situation will become even more fraught if Pakistan follows through on its threat to arm its surface vessels with nuclear weapons. In that scenario, some ships will carry nuclear weapons and some won’t. This ambiguity creates all kinds of new pathways for mistakes, misunderstandings, miscalculations, and mischief. If a missile is launched from one of these ships, how will India know whether it is a nuke or not?

“That will lead us to Armageddon,” warned Abhijit Singh, a former Indian naval officer and current senior fellow at the Observer Research Foundation, a New Delhi think tank.

The other big worry, especially with regard to Pakistan, is that nuclear weapons will somehow fall into the hands of terrorists. With Pakistan’s existing land-based arsenal, the warheads and missiles are stored separately in a series of heavily guarded secret locations. That can’t be done with ships and submarines. The weapons will instead have to be handled and stored at the Naval Dockyard in Karachi or at the newer Ormara facility in Balochistan, according to Rifaat Hussein, a security expert at Pakistan’s National University of Science and Technology, who recently toured the navy’s Ormara facility.

Either way, terrorists will know exactly where they have to go to get what they want, and al-Qaeda has already shown a willingness and capability to hit those facilities. Naval Station Mehran, a sprawling base in Karachi that is headquarters for the navy’s air fleet, is adjacent to the Pakistan air force’s giant Faisal base, a likely repository of nuclear components.

In 2011, a team of 15 to 20 heavily armed militants breached the security perimeter at Mehran, made their way to the heart of the base, and destroyed two P-3C Orion anti-submarine aircraft.

Pakistani commandos and security personnel spent nearly 18 hours fighting to retake the base, and at least 13 of them died in the effort. The Pakistani Taliban initially claimed responsibility, but later there were credible suggestions that al-Qaeda may have carried out the attack. Either way, the ease with which the attackers entered the base — and their focus on destroying the most valuable military assets — suggested they had inside help.

When the Mehran base came under attack, both Pakistan and India immediately put their nuclear assets on high alert because of its proximity to one of Pakistan’s key nuclear stockpiles. The incident left both sides uneasy about the security of their most destructive weapons.

“The Pakistan navy was always known to be a highly professional force. Now all of that seems to have changed,” Singh, the former Indian naval officer, told me. “The systemic infiltration of the navy by these radicalized elements is shocking to us,”

Although these incidents are cause for alarm, most experts agree that Pakistan has done a good job safeguarding its nuclear weapons. Protecting the nukes — from India, from homegrown terrorists, and from the US military, which has spent millions of dollars helping Pakistan secure its nuclear arsenal but still remains a suspect ally — is Pakistan’s highest priority.

The supervision of the nation’s nuclear arsenal is managed by an elite agency within the military called the Strategic Plans Division. Rising above the morass of Pakistan’s domestic politics, the SPD projects an image of calm professionalism. In Islamabad, I met with Brig. Gen. Zahir Kazmi, director of the SPD’s arms control and disarmament branch, who made the case that Pakistan “is very much alive” to the dangers of managing nuclear weapons at sea.

“We are confident but not complacent,” he said.

Kazmi recognized the responsibility of safeguarding the weapons in the face of a challenging domestic security environment but bristled at any suggestion from an American that Pakistan’s military might not be up to the task of protecting its most important assets.

“Managing nuclear safety and security is not a white man’s burden only,” he said. “Pakistan is managing its responsibilities quite well. There is a deliberate tendency to forget that Pakistan’s record is as good, if not better, than that of the US.”

America’s role in the growing numbers of nukes in the Indian Ocean has been one of muddled ambiguity. In 2008, the US signed a commercial agreement that allows India to share in most of the benefits of the Nuclear Suppliers Group even though India has never signed the Nuclear Non-Proliferation Treaty. This bending of the rules allows India to import uranium for civilian energy projects, freeing up domestic capacity for production of the highly enriched uranium (HEU) needed to fuel the reactors on its new submarines.

Last summer, the US signaled a sharper tilt toward India by conducting joint naval exercises in the Indian Ocean with India and Japan. This was meant as a warning to China, with its growing ambitions in the Indian Ocean, but it did little to calm anxieties in Pakistan.

Meanwhile, in his very first tweet of 2018, President Trump abruptly and unexpectedly cut off military aid to Islamabad.

“The United States has foolishly given Pakistan more than 33 billion dollars in aid over the last 15 years, and they have given us nothing but lies & deceit,” Trump tweeted on New Year’s Day. “They give safe haven to the terrorists we hunt in Afghanistan, with little help. No More!”

Aside from the oddity of conducting foreign policy via Twitter, the public scolding was taken in Islamabad as a humiliating insult, further complicating ties with an admittedly difficult but necessary US ally in Washington’s never-ending “war on terror.”

The cold war between India and Pakistan seems to be heating up

As the Indian Ocean arms race accelerates, both India and Pakistan are rethinking when and how they might take the nightmare step of launching the doomsday weapons at each other.

Their nuclear rivalry goes back to May 1998, when both countries shocked the world with a series of nuclear tests. Five years later, India declared its “no first use” doctrine. India’s political leadership has made clear that it views nukes as political weapons — a way to project global power and perhaps win a seat on the United Nations Security Council — not as war-fighting weapons. India’s military, however, has been frustrated by Pakistan’s tactic of allowing terror groups to fight a low-grade proxy war against India.

Pakistan calculates that it can use this tactic to hurt India without fear of retaliation because India would be afraid of provoking a nuclear response. The 2001 attack on India’s parliament building and the 2008 Mumbai attack are the most notorious examples of this.

Both were carried out by Pakistan-based militants with well-established links to Pakistan’s Inter-Services Intelligence agency, or ISI, the military’s powerful spy agency. Terrorism is the classic underdog’s tactic. Pakistan is clearly the underdog in any nonnuclear matchup with India, but it is certainly the world’s first nuclear-armed underdog to successfully apply the tactic against a nuclear rival.

Infuriated by what it sees as a kind of blackmail, India’s military is looking to develop strategies in which it could apply its superior conventional force to punish Pakistan without provoking a nuclear response.

Pakistan, meanwhile, has tweaked its nuclear doctrine from “credible minimum deterrence” to something it calls “full spectrum deterrence,” which apparently countenances the use of low-yield tactical battlefield nuclear weapons on its own territory in the event of an Indian incursion — another unsettling first in the annals of nuclear deterrence.

During the Cold War, the dynamic that drove the US-Soviet arms race was MAD — mutually assured destruction — which saw both sides accumulate vast arsenals with tens of thousands of warheads. The logic was that each side possessed such overwhelming destructive power that neither would ever dare use it. Both sides understood that a nuclear war would be unwinnable and, therefore, unthinkable. A reverse — and equally perverse — dynamic propels the India-Pakistan rivalry. As India searches for ways to use its overwhelming conventional military advantage, a nervous Pakistan is forced to keep lowering the threshold for nuclear retaliation.

As a result, there have been recent signals that India is rethinking or reinterpreting its no-first-use doctrine. A 2016 book by Shivshankar Menon, a respected national security adviser in the previous government, caused a stir by declaring “a potential grey area as to when India would use nuclear weapons first.” Menon suggested India would be prepared to order a preemptive strike if it appeared Pakistan was about to use its nuclear weapons.

Prime Minister Narendra Modi’s Hindu nationalist Bharatiya Janata Party floated a similar idea in 2014, urging a more flexible nuclear doctrine to deal with Pakistan. And while Modi himself says he remains committed to no first use, his previous defense minister, Manohar Parrikar, argued that India needed a less restrictive nuclear doctrine.

If nothing else, Indian generals are speaking much more aggressively since they completed the full nuclear triad, which gives them an assured way of hitting Pakistan even if India has been hit by a nuclear attack. In January, Gen. Bipin Rawat, the army’s new chief of staff, declared that India was prepared to test Pakistan’s threat to use nuclear weapons if a new war broke out.

“We will call their bluff,” Rawat said. “If given the task, we will not say we cannot cross the border because they have nuclear weapons.”

And that’s why this all matters so much for the two countries and their hundreds of millions of citizens — and the world as a whole. India and Pakistan are mortal enemies that have dozens of nuclear warheads aimed at each other. That was scary when those nukes were only on land. It’s a much scarier situation now that those nukes have been put onto submarines that move deep underwater, holding the deadliest payloads imaginable.

Tom Hundley is a senior editor at the Pulitzer Center on Crisis Reporting.

——--———————————————————————--—————--——--————--————————

Editor’s note. This story has been updated to include links to the work of Ankit Panda and Christopher Clary, two experts on the nuclear arms race between India and Pakistan. Additionally, there were a string of attacks on Pakistani air force bases in Sargodha and Kamra between 2007 and 2012, not just two incidents. Finally, the US Navy has 18 Ohio-class submarines, but only four are configured to fire cruise missiles.