But nuclear escalation can happen by accident too. "This could happen by human error, hackers, terrorists, computer failures, bad data from satellites and unstable leaders," Prof Alan Robock of Rutgers University, lead author of the landmark 2019 paper by a global team of scientists, told the BBC.
In March 2022, India accidentally fired a nuclear-capable cruise missile which travelled 124km (77 miles) into Pakistani territory before crashing, reportedly damaging civilian property. Pakistan said India failed to use the military hotline or issue a public statement for two days. Had this occurred during heightened tensions, the incident could have spiralled into serious conflict, experts say. (Months later, India's government sacked three air force officers for the "accidental firing of a missile".)
Yet, the danger of nuclear war remains "relatively small" between India and Pakistan, according to Mr Clary.
"So long as there is not major ground combat along the border, the dangers of nuclear use remain relatively small and manageable," he said.
"In ground combat, the 'use it or lose it' problem is propelled by the possibility that your ground positions will be overrun by the enemy." ('Use it or lose it' refers to the pressure a nuclear-armed country may feel to launch its weapons before they are destroyed in a first strike by an adversary.)
AFP via Getty Images A view of Chaghi district hill which turned white from top after Pakistan tested its five nuclear devices on May 28, in the southwestern Baluchistan province, 19 June. Prime Minister Nawaz Sharif visited the site first time after Pakistan's six nuclear explosions in response to nuclear detonations by rival India. (Photo credit should read ZULFIQAR BALTI/AFP via Getty Images)AFP via Getty Images
The Chagai Hills, whitened at the top after Pakistan's nuclear tests in May 1998, in south-western Balochistan
Sumit Ganguly, a senior fellow at Stanford University's Hoover Institution, believes that "neither India nor Pakistan wants to be labelled as the first violator of the post-Hiroshima nuclear taboo".
"Furthermore, any side that resorts to the use of nuclear weapons would face substantial retaliation and suffer unacceptable casualties," Mr Ganguly told the BBC.
At the same time, both India and Pakistan appear to be beefing up their nuclear arsenal.
With new delivery systems in development, four plutonium reactors and expanding uranium enrichment, Pakistan's nuclear arsenal could reach around 200 warheads by the late 2020s, according to The Nuclear Notebook, researched by the Federation of American Scientists' Nuclear Information Project.
And as of early 2023, India was estimated to have about 680kg of weapons-grade plutonium - enough for roughly 130-210 nuclear warheads, according to the International Panel on Fissile Materials.
Despite repeated crises and close calls, both sides have so far managed to avoid a catastrophic slide into nuclear conflict. "The deterrent is still holding. All Pakistanis did was to respond to conventional strikes with counter-conventional strikes of their own," writes Umer Farooq, an Islamabad-based analyst.
Yet, the presence of nuclear weapons injects a constant undercurrent of risk - one that can never be entirely ruled out, no matter how experienced the leadership or how restrained the intentions.
"When nuclear weapons can be involved, there is always an unacceptable level of danger,"John Erath, senior policy director at the non-profit Center for Arms Control and Non-Proliferation, told the BBC.
"The Indian and Pakistani governments have navigated these situations in the past, so the risk is small. But with nuclear weapons, even a small risk is too large."
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