The shortest and clearest answer to the question posed in the title is “Nobody knows.” To call the politics of South Asia “murky” is the understatement of the century.

The mainstream of opinion seems to prefer the theory that they were militant Islamists. Animesh Roul over at Counterterrorism Blog posits that they may have been Kashmiri militants (specifically  Lashkar-e-Toiba) impersonating homegrown Indian jihadis (hence the “Deccan Mujahideen”, a group nobody had ever heard of, claiming responsibility).

However, there are others who believe that they were actually militant Hindus impersonating Islamists and therefore trying to inflame sentiment against Pakistan. To make your head spin a little more,  it may also have been militant Islamists pretending to be militant Hindus pretending to be militant Islamists in an effort to frame militant Hindus.

The odds are that it may actually end up being some combination of all of the above. As Aaron Mannes puts it,

The reality is that the structures supporting this attack go beyond specific organizations.

In other words, the gunmen were most likely pawns, and the organization(s) from which they came and the networks that equipped them were most likely pawns as well.

Pawns of whom? Depends on who has the most to gain from the ultimate fallout, which isn’t clear just yet but is starting to take shape:

“We will increase security and strengthen it at a war level like we have never done it before,” Sriprakash Jaiswal, India’s minister of state for home affairs, told Reuters on Sunday.

“They can say what they want, but we have no doubt that the terrorists had come from Pakistan,” Jaiswal said.

An official in Islamabad said the next one to two days would be crucial for relations.

And who benefits from that? From the same article:

Officials in Islamabad have warned any escalation would force it to divert troops to the Indian border and away from a U.S.-led anti-militant campaign on the Afghan frontier.

The point of a terrorist attack is not the attack itself; it’s the reaction. The aftermath of the 9/11 attacks saw the U.S. react like a wounded bull, get bogged down in an unwinnable war that’s bled us dry militarily, and absolutely shred our credibility around the world. To borrow a phrase, mission accomplished.

So what’s the goal here? Probably what’s stated above: take the heat off of the Afghan frontier. Whatever the goal is, it’s a safe bet that whoever’s ultimately responsible for the Mumbai attacks could care less about anything that actually happens in Mumbai. The city  – and the hundreds of dead human beings – just made a convenient target.