Protesters decry Thursday’s attack on a paramilitary convoy, in the Jammu and Kashmir region in India Friday. (Channi Anand/AP) By Asfandyar Mir February 15 at 11:30 AM On Thursday, a suicide car bomber launched a major terrorist attack in Indian Kashmir. In the town of Pampore, a vehicle armed with a bomb rammed into a bus full of Indian paramilitary soldiers, killing 44 and injuring several others.

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Although insurgent violence against military targets in Kashmir is not without precedent, here’s what’s different: This attack is the deadliest single incident in decades involving Indian security forces.

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The attack has India rattled — and pointing fingers at Pakistan . This is troubling because India and Pakistan have fought multiple wars over Kashmir besides being engaged in intermittent skirmishes along the border. Will the Pampore incident spark a new and dangerous phase in the enduring rivalry between nuclear-armed India and Pakistan? Here’s what you need to know:

1. Who is responsible?

Militant group Jaish-e-Muhammad (JeM) , a group that aims to unite Kashmir with Pakistan, has claimed responsibility for the attack. According to JeM, the bomber, Adil Dar, hails from a town near the site of attack. This is not unusual for Kashmir, where Indian authorities are concerned about a spike in young recruits joining jihadi groups operating in the region. In the Kashmir valley, anger and resentment toward the Indian government has deepened in recent years — especially as the government has employed violent repressive tactics.

JeM’s claim of responsibility makes the situation especially volatile. JeM is a sophisticated group , with a base in Pakistan and a history of salient attacks in India. It carried out the 2001 attack on the Indian parliament in New Delhi, and the 2016 attack on an Indian Air Force base in the city of Pathankot.

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Though officially banned by the Pakistani government, JeM has operated from Pakistan for two decades, which suggests it has close links to Pakistan’s security establishment. JeM has also helped Pakistan in its own war against terrorist groups like the Tehree-e-Taliban Pakistan. At the United Nations, at Pakistan’s behest, China has repeatedly blocked JeM’s designation as a terrorist group.

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Given Islamabad’s ban-yet-support approach toward JeM, many in India and beyond are likely to see the Pakistani security establishment as having sponsored the Pampore attack. Pakistan has denied any involvement , and will continue to do so. Pakistan might offer to investigate cross-border links of the attackers and arrest some JeM leaders for the time being. However, given the bad blood between the two countries on investigations of similar attacks, it is equally likely that Pakistan may outright refuse to respond

2. What happens next in South Asia?

On Friday, Indian Prime Minister Narender Modi pledged a strong response

But the Pampore attack revives India’s strategic dilemma on Pakistan-based militant groups: how to retaliate without risking a nuclear war. The urge to act is particularly serious, given Modi’s long-standing pledge to punish Pakistan for supporting terrorism on Indian soil

Modi is also up for reelection this year, which in recent months has increasingly looked like an uphill battle. As political scientists Vipin Narang and Paul Staniland point out, no foreign policy issue rallies the Indian electorate like anger toward Pakistan. If the Modi government does nothing in response to the attack, it is likely to incur domestic political costs

What response options might India consider? In 2001-2002, Indian policymakers undertook a massive troop mobilization along the international border with Pakistan, threatening all-out war. In 2016, India claimed to have carried out a small-scale incursion as a retaliation for an armed attack on an Indian military camp in the border town of Uri. India has also considered airstrikes and artillery fire on Pakistani military and intelligence positions deep in the Pakistan-controlled part of Kashmir, as well as a large-scale rapid attack in mainland Pakistan.

But Pakistan can thwart some of these options . It has a favorable defensive position in Kashmir, which suggests it could limit the damage from small-scale Indian incursions. Back in 2001, Islamabad responded to a large-scale Indian troop mobilization with its own mobilization, and held its ground. In recent years, Pakistan has developed small-scale battlefield nuclear weapons  — called tactical nuclear weapons — and threatens to use them in case of a large-scale Indian attack against advancing forces

This means any Indian military action comes with a risk of serious — and potentially difficult to control — escalation of hostilities between the two nuclear-armed foes

This is not to say India will be deterred. Many Indian policymakers, including the army chief, argue that Pakistan’s capabilities are overstated  — despite warnings by some officials that the Pakistani reaction might be difficult to manage. And Modi has political incentives to act. He is likely to assess this uncertainty, gauging the high domestic political cost of not acting against the potential risks of military action. The chance of serious Indian use of force against Pakistan is real

3. What will be the U.S. response?

The White House issued a statement to condemn the Pampore attack — but Washington is in an awkward position. The United States wants Islamabad’s help to end the war in Afghanistan, and senior U.S. officials have cautiously praised Pakistan’s help in recent months toward the Afghan peace process. President Trump’s emphasis on a pullout from Afghanistan increases Pakistan’s importance to U.S. regional policy

The United States would be hard pressed to sanction Pakistan for terrorism emanating from its soil — or back an Indian military operation into Pakistan. The U.S. government might continue to condemn Pakistan for providing terrorist groups with a safe haven but that would be the possible extent of its support for India. As important as the long-term India-U. S. relationship may be in the eyes of U.S. strategists, the needs of the conflict in Afghanistan — and Pakistan’s role there — are likely to take precedence in the short run

Asfandyar Mir is a postdoctoral fellow at the Center for International Security and Cooperation  at Stanford University.