When Indian war planes rocketed into Pakistani territory on Tuesday, unleashing an attack on what India claims were terrorist targets, it was the first time India had launched air strikes on Pakistani soil since 1971. In the 48 years since that time—when India entered the war that turned East Pakistan into the independent Bangladesh—something has changed between the two rival South Asian powers: India and Pakistan are both now armed with nuclear weapons. So, as Pakistan has returned fire, shooting down two Indian jets on Wednesday, one of the most important questions in the world has become: What stops this conventional conflict between the two nations from escalating into a nuclear war?
Since 1974, when India shocked the world with its surprise nuclear test of the "Smiling Buddha" weapon, South Asia has been a nuclear hot spot. However, like China, India maintains a "No First Use" doctrine, which states that India will only use its nuclear weapons in response to a nuclear attack. The policy was declared in 1999, a year after Pakistan successfully detonated five of its own nuclear weapons, deep inside a mountain in southern Pakistan. Since then, Pakistan has refused to issue any clear doctrine governing its own use of nuclear weapons. In other words, no one—outside of Pakistan's highest command—knows what could provoke the nation to launch a nuclear strike.
In 1999, Pakistan's foreign minister explained why the country refused to adopt a No First Use policy, declaring that Islamabad would use "any weapon" in its arsenal to defend the country. Today, experts believe that, unlike India, Pakistan could plausibly deploy a nuclear weapon in response to a conventional attack. Pakistan maintains a smaller army and less weaponry than India, and would likely be overwhelmed if the Indian military invaded Pakistani territory with its full force. Facing loss of territory and national collapse, Islamabad could decide to launch a nuclear weapon against India in an attempt to even the playing field. In an analysis of his country's nuclear doctrine in 1999, Sardar F.S. Lodi, a former Pakistani lieutenant general, wrote:
In a deteriorating military situation when an Indian conventional attack is likely to break through our defences or has already breached the main defence line causing a major set-back to the defences, which cannot be restored by conventional means at our disposal, the government would be left with no other option except to use Nuclear Weapons to stabilize the situation.
Lodi wrote his analysis as an outside commentator, not an official representative of the Pakistani state. To this day, Pakistan's nuclear doctrine remains ambiguous, in what many experts consider to be a deliberate choice. ("If Pakistan has not released a nuclear doctrine, it does not mean that it has not got one. It is understandable that a small nuclear power that espouses a limited aim of deterring coercion from a larger neighbour, maintaining calculated ambiguity would be a rational choice," Hasan Ehtisam, a scholar on Pakistani security policy, wrote in a Pakistani newspaper last year.)
Does that mean the current conflict between Pakistan and India could escalate into a nuclear confrontation? Commentators regard that possibility as unlikely. Pakistan first began developing nuclear weapons in response to its humiliating loss of territory in 1971. Thus far, the current conflict with India does not appear to be a land grab, which suggests Pakistan does not have reason to engage its nuclear option.
"To be clear, escalating tensions to the point of nuclear conflict would be catastrophic for both India and Pakistan and would destabilize the entire region—an option unlikely to be taken by either New Delhi or Islamabad," Saheli Roy Choudhury wrote for CNBC on Wednesday.
History bolsters Choudhury's analysis. In 1999, Pakistan and India became the first nuclear powers ever to engage in direct war with each others' forces. On the ice of the Kargil Glacier, nestled nine miles above sea level between Himalayan peaks, Pakistani soldiers, initially disguised as a Kashmiri militants, exchanged fire with Indian soldiers. The high-altitude fighting only lasted two months before the two sides agreed to de-escalate. But in 2002, a former White House aide revealed to the BBC that United States satellite imagery in 1999 had shown the Pakistanis deploying nuclear weapons for potential use. According to the former aide, Bruce Riedel, the U.S. immediately launched a diplomatic effort to dissuade Pakistan's use of nuclear weapons and to de-escalate the conflict.
On Wednesday, the U.S. diplomatic apparatus was mainly focused on Hanoi, Vietnam, as President Donald Trump met with North Korean dictator Kim Jong-Un to try to de-escalate nuclear tensions on the Korean Peninsula. With the focus on the Hanoi summit, observers remain unsure of what role the U.S. has the capacity to play in defusing hostilities between Pakistan and India. Though the European Union and United Nations Security Council have preached caution and de-escalation, neither India nor Pakistan has issued a conciliatory statement.