NEW DELHI (NYTIMES) - For the first time in five decades, Indian warplanes crossed into Pakistan and conducted airstrikes on Tuesday (Feb 26). But in the jarring escalation of hostilities, the leadership of each nuclear-armed country also appeared to leave itself a way out of pushing the conflict into war.

In India, where election-year nationalism is fueling waves of anger over the militant attack in Kashmir that killed dozens of soldiers this month, the story line was of righteous vengeance accomplished.

"We won't let this country bow down!" Prime Minister Narendra Modi told a charged rally in New Delhi, speaking in front of a backdrop with the photos of the Indian soldiers killed by a suicide bomber.

In a statement, India's foreign ministry claimed that airstrikes near Balakot in northern Pakistan had struck "the biggest training camp" of Jaish-e-Mohammad, the group that claimed responsibility for the suicide bombing, killing a "very large number" of militants as they were planning another attack.

But in Pakistan, where the domestic tone has been one of fatigue over enduring economic crisis and political ennui, the country's military command insisted that India's air incursion had achieved nothing.

Prime Minister Imran Khan promised a response to the strikes, which he dismissed as a political ploy by Mr Modi, carried out for "domestic consumption" before national elections. He shrugged off Indian claims that the airstrikes had resulted in "heavy casualties" or struck a militant training camp, according to a statement issued by his office.

In a sign of escalating tensions, Mr Khan summoned the National Command Authority - the body that oversees the deployment and management of Pakistan's nuclear arms - for a special session on Wednesday (Feb 27). The prime minister also called for Parliament to meet on Wednesday to discuss a response.

With India claiming to have avenged the Kashmir attack, and with Pakistan claiming that India had done no real damage, it seemed possible that the situation could yet be defused. Still, analysts cautioned that the crisis could erupt into something more serious if restraint failed on either side.

Mr Ikram Sehgal, a defence analyst with ties to Pakistan's national military establishment, said the country's response to the strikes would be "measured".

But he added: "The only question is will India's leadership be able to stomach it and whether we will go into a dangerous territory of further escalation."

Residents around Balakot, the scene of the attack in Pakistan, said they saw no sign of any significant damage from the airstrikes.

Pakistan's chief military spokesman, Major General Asif Ghafoor, portrayed the incursion as a high-speed dip in and out by Indian jets as they were confronted by Pakistani fighter planes.

He later posted on Twitter four images of a forested area pockmarked with small craters and debris, which he said was the site of Indian airstrikes.

The view that little had been damaged was supported by military analysts and two Western security officials, who said that any militant training areas at the site, in the Pakistani province of Khyber-Pakhtunkwha, had long since packed up or dispersed. (Earlier reports had placed the attack in the Pakistani side of Kashmir, which is nearby.)

The suicide bombing by Jaish-e-Mohammed, on Feb 14 near Pulwama in Kashmir, was the deadliest in the region in decades, at a time when a heavy Indian security presence has been trying to stamp out any signs of insurgency in the disputed territory.

India swiftly blamed Pakistan, which has a history of fostering militant proxies, for directing the attack. But Pakistani officials denied that Jaish-e-Mohammed had the freedom to operate within Pakistan. And Mr Khan insisted that Pakistan would investigate the attack if India offered evidence.

Through decades of tensions, Pakistan and India have gone to war over Kashmir twice, and have pushed to the edge of it many times. The brinkmanship has evolved into a dangerous but almost formalised language of escalation and de-escalation over the years.

News of the strikes on Tuesday sparked panic on both sides of the border, with Indian and Pakistani residents either fleeing their homes or stockpiling food, fearing a larger outbreak of war.

Though India and Pakistan routinely shell each other across the Line of Control, this is the first time since the countries' war in 1971 that either side has confirmed sending warplanes into the other's airspace.

A resident of Attar Shisha village inside Pakistan, about 3.2km from Balakot, said he was woken up by loud explosions about 3.15am on Tuesday. He was reached by phone, and asked to remain anonymous out of fear of reprisal by the Pakistani authorities.

The villager said that Jaish-e-Mohammed still ran a school in Balakot, but that the airstrikes missed the facility and hit an empty ravine instead, adding that there were no casualties he had heard of.

Across the disputed border, hundreds of Indians fled their villages and towns scattered along the Line of Control on Tuesday, after fearing for days that tensions would only escalate.

"We first heard the sound of aircraft hovering above at around 2am. We could not sleep," said Mr Imran Khatana, a farmer from Salamabad village in Indian-controlled Kashmir. "I pushed my family members into a bunker thinking something wrong is going to happen."

Mr Khatana said there had been a buildup of Indian troops over the last few days along the border. Residents of Kashmir rushed to markets to buy essential supplies, worried that tensions would worsen. A major hospital in Srinagar cancelled staff holidays and asked employees to be on standby.

Balakot and its surrounding area hosted numerous militant training camps until 2005, when a powerful earthquake struck the area, devastating its towns and villages. As international aid groups poured in to provide relief, militants packed up their camps and went elsewhere, to avoid being detected, analysts say.

Some worried that the Indian incursion, effective or not, still carried a high risk of military reprisal from Pakistan.

"The Pakistanis are bound to react, conventionally and not through a proxy like a militant group," said Mr Rahul Bedi, an analyst at the London-based Jane's Information Group, which tracks the defence industry. "Where they react and when is something that only Pakistanis know."

The US government has typically been a broker between India and Pakistan, conducting shuttle diplomacy in similarly heated situations. But President Donald Trump has taken a hard line on Pakistan while drawing closer to India since coming to office in 2017.

From China, which has traditionally supported Pakistan in moments of international pressure, the message was studiously neutral, calling for restraint from both sides and prioritising the importance of fighting terrorism.

"A sound relationship and communication serve the interests of both countries and the stability of South Asia," said Mr Lu Kang, a spokesman for the Ministry of Foreign Affairs. "Fighting against terrorism is a global challenge and needs international cooperation."

India controls much of Kashmir, while Pakistan controls a smaller part of the region, which was left in an undetermined state after the British partition of India in 1947. It has seen decades of violence from militants seeking independence.

In the run-up to Indian elections this spring, and with Mr Modi facing a fierce re-election fight, voters have demanded that New Delhi respond to the Kashmir attack with force against Pakistan.

"What they hit is speculation for now - they say they hit a terrorist camp, but a lot of intelligence sources say those camps in Pakistan had been cleaned out in recent days," Mr Bedi said.

"This is more political symbolism than anything else. Mr. Modi had to show some demonstrable action on India's part, ahead of elections."