When Pakistani Taliban gunmen stormed a school in December 2014, killing more than 130 schoolboys, it united many Pakistanis in support of a major offensive against the radical group that had been growing more menacing for years.

That military operation, which was already underway, picked up momentum. Violence is down, and Taliban have been weakened in their strongholds in northwest Pakistan, near the border with Afghanistan.

Yet Pakistan is still vulnerable, as demonstrated bya suicide bombing on Easter Sunday at a crowded park in the eastern city of Lahore, which killed more than 70 people and injured hundreds more.

"The target were Christians," said Ehsanullah Ehsan, a spokesman for the Taliban faction Jamaat-ul-Ahrar, Reuters reported. "We want to send this message to Prime Minister Nawaz Sharif that we have entered Lahore. He can do what he wants, but he won't be able to stop us. Our suicide bombers will continue these attacks."

The claim was being taken seriously, though not as absolute proof in a country where multiple groups sometimes claim the same attack. Pakistan's government did not immediately say who it thought was responsible.

The country is riddled with fault lines. Sunni and Shiite Muslims resort to sectarian violence. The megacity of Karachi is a cauldron of rival political and ethnic factions. While Pakistan's main battle pits the Taliban against the government, even here there are twists.

The Jamaat-ul-Ahrar faction broke away from the Taliban a couple of years ago, but re-established at least nominal links last year.

All of these complications make it difficult to determine exactly what the latest attack means in terms of the larger battle.

Christians Say They Receive Little Protection

Pakistan's Christians are attacked periodically, though usually not with such ferocity. They account for around 2 million of Pakistan's 190 million people and have no economic or political clout. They often complain that the government does little to protect them.

Many Christian families were in Lahore's Gulshan-e-Iqbal park on Sunday evening to celebrate Easter when the bomber struck. However, reports suggested the vast majority of the dead and wounded were Muslims, many of them women and children in a play area where kids were riding merry-go-rounds.

Joe Francis, a leader in Lahore's Christian community, said it was not clear how many of the dead and injured were Christians. But he said when he learned of the attack, "it immediately occurred to me that this was an attack on Christians. Anybody who sees these scenes has to get furious, no matter whether he is Hindu, Muslim or Christian."

NPR's Philip Reeves visited the nearby Sheik Zayad Hospital and reported that many of those wounded were children, some as young as 2.

"There are 14 kids on this list who are being treated for injuries, and this is just one of the city's hospitals, so it's clear that children have been particularly hard hit in this attack," he told Morning Edition.

The bombing was also seen as a message both to Sharif, the prime minister, and the military engaged in the operation against the Pakistani Taliban.

"Since mid-2014, Pakistan's armed forces have been carrying out a major and almost completely unreported war against Islamist militants," Reeves reported. "The focus of this is the tribal belt bordering Afghanistan, although the security forces also carried out a big crackdown in the city of Karachi."

While there's a broad consensus that the Taliban have been set back, and attacks have gone down, the group is still potent. And the cost of the military action has been high, measured both in casualties and in the destruction of many civilian areas, driving families from their homes.

Lahore As A Target

A major attack in Lahore is also significant.

Sharif is from Lahore, and it's his political base. His younger brother, Shahbaz Sharif, is the chief minister of Punjab province, where Lahore is the capital.

"Those who targeted innocent citizens do not deserve to be called humans," Shahbaz Sharif said on Twitter. "We will hunt you down,"

The eastern city is the most cultured and cosmopolitan in Pakistan and has been largely spared the violence of other cities. For many years, Lahore saw itself as largely immune from the religious and political passions playing out in the northwest or down south in Karachi.

But Pakistani security officials and analysts have stressed that the Taliban and other extremist groups have been drawing recruits from Lahore and other parts of Punjab province, the country's most populous region.

Ahmed Jan, a university lecturer in Lahore, said the crackdown had improved the sense that Pakistan was gaining the upper hand against the militants.

"There was this feeling that perhaps suicide bombings would become a thing of the past, but I think it hit home last night that the war is very much an ongoing effort," he said. "Who knows whether we're winning or losing this war."

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