Weeks of tension erupted early on Wednesday morning when India fired missiles into Pakistan and Pakistan-controlled Kashmir, escalating the likelihood of a full-blown military confrontation between the nuclear-armed South Asian neighbours.
Pakistani authorities said at least 19 people, including a child, were killed overnight, decrying a "blatant act of war".
India said its strikes were "focused, measured and non-escalatory in nature", emphasising that no Pakistani military facilities had been targeted.
Police in Indian-controlled Kashmir later said at least 10 people had been killed by retaliatory Pakistani shelling.
New Delhi blamed Muslim-majority Pakistan for a terror attack last month in Indian-controlled Kashmir that killed 26 Hindu tourists — the deadliest violence against Indian civilians since the 2008 Mumbai attacks.
Indian Prime Minister Narendra Modi pledged to hunt "terrorists and their backers … to the ends of the earth".
Pakistan's government denied any involvement.
Australian Strategic Policy Institute resident senior fellow Raji Pillai Rajagopalan said there was a "a lot of disappointment, pain and anger" in India over the religion-based targeting of civilians.
"India could not have gone without responding to this particular situation," she said.
So, how does this situation compare with past conflicts?
And now that India has launched an assault, what happens next?
How did we get here?
Muslim-majority Kashmir is claimed by both India and Pakistan, with both countries controlling parts of the region separated by the Line of Control, the de facto border.
The two countries fought wars in 1947-8, 1965, 1971 and 1999 and have clashed numerous times, most notably over Kashmir.
"We have actually seen this film play out before," said the Washington-based Hudson Institute's India Initiative director Aparna Pande.
"Every few years there's a terror attack inside India, which is almost always tied to a Pakistan-based terror group, there's an escalation in tensions.
"Since 2016 India has chosen not to restrain itself but conduct strikes … then Pakistan responds, and normally the international community comes in and de-escalates tensions," she said.
"Both countries then after a few years have conversations, then again a terror attack takes place. So this is a cycle on repeat."
Amit Ranjan, a research fellow at the National University of Singapore's Institute of South Asian Studies, said in the 1999 Kargil war between India and Pakistan, fighting was mostly confined to mountainous areas so the civilian cost was minimal.
But given Pakistani civilians had already been killed, it appeared to be a different scenario this time around, he said.
"If missiles start raining between the two countries, civilians may be affected," he said.
"When you have civilian casualties it becomes a bit difficult for anyone to not retaliate."
Will India and Pakistan go to war?
Pakistani Prime Minister Shehbaz Sharif said on social media: "The treacherous enemy has launched a cowardly attack on five locations within Pakistan.
"This heinous act of aggression will not go unpunished. Pakistan reserves the absolute right to respond decisively to this."
Pakistan's Defence Minister Khawaja Asif claimed five Indian planes had been shot down and that Indian soldiers had been captured.
Speaking to Bloomberg TV, Mr Asif denied that there were terrorist training camps in the areas struck by India and that it was civilians who were suffering.
"This has been initiated by India … If India backs down we will definitely wrap up this thing," he said.
"But as long as we are under attack, under fire, we have to respond. We have to defend ourselves."
Experts said the course of the conflict depended on the scale and nature of Pakistan's response.
RAND Corporation defence analyst Derek Grossman told the ABC that the air strikes were "a very serious escalation in India-Pakistan tensions that could, if taken to the extreme, result in nuclear war".
"Much depends on the Pakistani response, and if they stay true to their word, then their retaliation may be substantial and potentially escalatory," he said.
"It's unclear how long this conflict will last, but both sides have a clear incentive to ensure it does not get out of hand and to the nuclear level."
What are the broader regional and global risks?
The two countries possess comparable nuclear arsenals, with India holding 172 nuclear warheads and Pakistan 170.
"There is a chance, though low, that an escalating war could bring great powers into conflict via proxy as well," Mr Grossman said.
"India benefits from Russian assistance in the form of defensive weaponry, with the Kremlin reportedly recently having provided new missiles," he said.
"However, India also has a strong relationship with the United States, and it has pledged support as well. And Pakistan's closest strategic partner is China."
Still, Dr Rajagopalan said Pakistan's leadership had "shown a reasonable amount of maturity to keep the conflict in limited fashion and not let it completely go out of hand".
"One can expect some retaliatory strikes from their side … [but] both the Indian and Pakistani political leadership do know the limits of this particular conflict, that they cannot escalate it to a nuclear level."
Pakistan also faces major economic challenges that could inhibit even any conventional war effort.
Moody's Ratings warned on Monday that prolonged conflict with India would hurt its economic growth.
By contrast, Moody's did not project significant economic consequences for India apart from the effect of higher defence spending on the government's fiscal position.
