Indian and American officials are now reporting that the Mumbai attackers seem to have connections to Lashkar-e-Taiba, the Pakistan-based Islamist organization. Among other analytical clues, over the weekend, one anonymous American official quoted in the Washington Post noted that Lashkar has a known “maritime” capability. I’m not sure how much seaworthiness a group needs to demonstrate in order to be labeled “maritime” terrorists, but I can testify to the existence of Lashkar’s pontoon boat fleet, as I was not too long ago a passenger on that line.

Late in 2005, I travelled for The New Yorker to Pakistan-occupied Kashmir to report on the earthquake that devastated the region. To facilitate international aid, the Pakistani government opened the region to journalists, creating a very rare opportunity to travel without escort and to poke around on the border. I was particularly interested in looking up Lashkar, which I had been following for many years. I made several visits to facilities run by its charity, called “Jamat-ud-Dawa,” which is today tolerated openly by the government of Pakistan but banned as a terrorist organization by the United States on the grounds that it is merely an alias for Lashkar.

In Muzuffarabad, the capital of Pakistani Kashmir, Jamat had brought in a mobile surgical unit staffed by long-bearded doctors from Karachi and Lahore—very impressive young men, fluent in English, who offered a reminder that unlike, say, the Taliban, Lashkar draws some very talented people from urban professions. (With its hospitals, universities, and social-service wings, Lashkar is akin to Hezbollah or Hamas; it is a three-dimensional political and social movement with an armed wing, not merely a terrorist or paramilitary outfit.) As part of its earthquake relief work, Lashkar ferried supplies to remote villages isolated on the far side of the churning Neelum River, one of the two snow-fed canyon rivers that traverse the area. I asked to take a ride with its volunteers, and their media officer (yes, they have media officers) agreed.

We rode in a van to the river’s edge, scrambled down a rocky hillside and boarded one of Lashkar’s rubber pontoon boats, about fifteen feet long, with a large outboard motor—useful for carrying relief supplies, but not coincidentally, also useful for infiltrating militants into Indian-held Kashmir. It has long been an open secret, and a source of some hilarity among foreign correspondents, that under the guise of “humanitarian relief operations,” Lashkar practiced amphibious operations on a lake at its vast headquarters campus, outside Lahore. The events in Mumbai have taken the humor of these “humanitarian” rehearsals away. That day on the Neelum, I chatted with our thick-bearded captain in my very poor Arabic. He spoke Arabic as well—from his religious studies, he said, although he conceded, too, that he had travelled to Saudi Arabia, where it is well understood that Lashkar has raised money. I was also told that around the time of the earthquake they set up fund-raising operations in Britain, to tap the Pakistani diaspora there.

Earlier this year, I met with a Lashkar official in Lahore. We talked about how Jamat was getting along under international pressure. I took no notes and the conversation was intended for my informal guidance, but I came away with a number of impressions. On the one hand, the group’s bank accounts remain unmolested by the Pakistani government, which gives Lashkar quite a lot of running room; on the other, the group resents the accommodations reached between Pakistan’s government and the United States. Clearly, Lashkar knows what it must do to protect the Pakistan government from being exposed in the violent operations that Lashkar runs in Kashmir and elsewhere. For example, some of its younger volunteers wanted to join the fight with the Taliban in Western Pakistan and Afghanistan, my interlocutor said, and so Jamat had evolved an internal H.R. policy by which these young men would turn in their Jamat identity cards and go West “on their own time,” much as think tanks allow policy scholars to take leaves of absence to advise political campaigns.

One question that will certainly arise as the Mumbai investigations proceed is what the United States should insist the government of Pakistan do about Jamat and Lashkar. Even for a relative hawk on the subject of Pakistan’s support for Islamist militias, it’s a difficult question—comparable to the difficult question of managing Hezbollah’s place in the fragile Lebanese political system. To some extent, Pakistan’s policy of banning Lashkar and tolerating Jamat has helpfully reinforced Lashkar’s tendency toward nonviolent social work and proseltyzing. In the long run, this work is a threat to the secular character of Pakistan, but it is certainly preferable to revolutionary violence and upheaval right now. On the other hand, there is little doubt that the Army and I.S.I. continue to use Jamat’s legitimate front as a vehicle for prosecution of a long-running “double game” with the United States, in which Pakistan pledges fealty to American counterterrorism goals while at the same time facilitating guerrilla violence against India, particularly over the strategic territory of Kashmir, which Pakistan regards as vital to its national interests.

Lashkar is a big organization with multiple arms and priorities and its leadership is undoubtedly divided over how much risk to take in pursuit of violent operations in India, particularly given the comfort and even wealth the group’s leaders enjoy from their unmolested activities inside Pakistan. If the boys in Mumbai had support from Lashkar, did the group’s leader, Hafez Saeed, who runs Jamat, know of the plan? If so, that would be a radical act that would likely mean the end of his charity’s tenuous legitimacy.

If it can be credibly established that Saeed did not know—that this was a rogue operation of some sort, or a strategy cooked up by elements of Lashkar and groups such as the Pakistani Taliban or even Al Qaeda (perhaps conducted, too, with support from rogue elements of the Paksitan security forces)—that would be an even more complicated equation. I was at a conference this morning where another panelist well-versed in these issues said he would not be surprised if it turned out that Lashkar conceived the Mumbai attacks as a way to pull Pakistani Army units and attention away from the Afghan border and into defense positions in the east, to protect the country from the possibility of military retaliation by India. In any event, if the evidence does show that uncontrolled Lashkar elements carried out the attacks, it would force India’s government to judge how to calibrate policy toward a civilian-led Pakistan government and Army command that may have little control over the very same Islamist groups that it purposefully built up and supported just a few years ago. If the evidence shows that these were purposeful attacks endorsed by Saeed and aided by elements of the Army, then the Pakistan government will have no choice but to at least make a show of closing down Jamat and arresting Saeed. Unfortunately, it has taken such action in the past, but that action has turned out to be partially symbolic and constructed for international consumption, rather than marking a true and complete change in policy.

The U.S. can do a few useful things here. At a minimum, it can provide transparent information about the investigation and where the facts lead, so that the Indian and Pakistani political systems are on the same footing; it can indict individuals and groups that can be established as culpable for the Mumbai murders, no matter who those individuals and groups are—even if they include officers in the Pakistan Army; and it can emphasize in public that the United States seeks the end of all Pakistani support for terrorist groups, no matter whether they are operating in Afghanistan, Kashmir, or Mumbai.