[cross-posted from CNN's Security Clearance blog]

By CNN's Nick Paton Walsh in Islamabad, Pakistan

Whatever peace process there was in Afghanistan, there is probably little left today.

The assassination Tuesday of Professor Burhanudin Rabbani in his home by at least one suicide bomber who hid a device in his turban hasn't just again reminded residents of Kabul that even the safest areas are vulnerable to insurgent attacks. It's surely made insurgents who have even the slightest whimsy to negotiate think again.

The war in Afghanistan is, by NATO's own admission, one of perception. And things aren't being perceived particularly well right now. Just over a week ago, NATO's headquarters and the U.S. Embassy came under a sustained attack that some residents said seemed to need 20y hours to totally suppress.

And just back in July, the half-brother of President Hamid Karzai - Ahmed Wali Karzai - was killed, also in his home, by another man who was thought to be friend, not foe. There are fewer reasons every day for Afghans to throw their weight behind the Americans, who are busy throwing their weight behind a timetable for departure.

"I think what you're seeing here is a deliberate attack by elements in the Taliban to make Kabul look unsafe, that the capital of Afghanistan is not a safe place, that no one is secure there, including the head of the peace council and a former president," said Bruce Riedel, a Middle East expert at the Brookings Institution in Washington.

Rabbani's death is a pretty remarkable event in the progress of the war. The first question is: who to blame? The Taliban's usually smooth system for claiming responsibility for attacks (SMSes, e-mails), for many hours remained silent. Their first utterance claimed responsibly but said they would need a little longer to reveal details - a departure for a group who've previously released the names of their attackers hours after they strike.

That dubiousness could point to the Haqqani network, the Pakistan-based, and some say Pakistan-backed, militants who have allegedly been behind many of the recent high-profile attacks in Kabul. They're less flamboyant about taking responsibility for things. But silence doesn't itself help assign guilt.

The truth is that any of the myriad of factions in an insurgency splintered by nearly a decade of war could have wanted this to happen. The word of peace talks was, in reality, more talk about talks as to whether there could be talks. The big question also remained: Would it really be possible, even if Mullah Omar's Quetta Shura wanted to strike a deal, to convince the younger fighters on the ground that such a deal was in their immediate benefit?

The Haqqani network, long seen as the brutal proxy of Pakistan's intelligence services, may have been fulfilling the old axiom that Pakistan doesn't want any peace it's not part of. That's allegedly led to the arrest in Karachi of Mullah Baradar, a Taliban leader said to have been seeking peace with the Americans without the oversight of his Pakistani connections.

In life, many also point out, the role Rabbani played as a powerful Tajik at the head of the peace council may have kept many Pashtuns from beginning peace talks. The role his death plays in mapping out Afghanistan's messy future will reveal itself in the coming months.