Is Pakistan intelligence implicated in Afghanistan bombings?
One of the main theories being investigated by western forces in Afghanistan is that Tuesday's bombing aimed at Shia targets, which killed 58 people, was carried out by the Haqqani network.
If this is true, it would point the finger at Pakistan's Inter Services Intelligence agency, which has nurtured a long relationship with this Afghan group, and has been publicly accused by the US of using it to orchestrate terrorist attacks in Kabul.
In September, Admiral Mike Mullen, the outgoing Chairman of the Joint Chiefs of Staff, told a Senate committee that the US had "credible intelligence" that the Haqqani network had carried out spectacular strikes in Kabul, including against the American Embassy, and that it acted as a "veritable arm" of the ISI. Pakistan slammed the comments as "irresponsible" and denied the accusation, in effect, of state backed terrorism.
However there have been a number of indicators that suggest the latest attacks may also have sprung from the Haqqani network. The staging of a coordinated multiple bombing operation (with targets in Kabul, Mazar-i-Sharif and Kandahar) is beyond the capabilities of almost all Taliban groups.
The mainstream Taliban, or Quetta Shura, have denied responsibility for Tuesday's bombings. In previous assaults on the Intercontinental Hotel and US Embassy, the Haqqani network has shown the capability to mount ambitious, coordinated, strikes.
The relationship between this group and the ISI goes back to the Soviet war, when the Pakistanis channelled weapons to its patriarch, Jalaludin Haqqani, who commanded forces in the border area around Tora Bora.
So what could the ISI's possible motive be for endorsing such a move, particularly when Pakistan's own Shia/Sunni tensions have historically been a good deal more aggravated than those in Afghanistan?
The ISI is often accused of acting autonomously from the government, but at this moment the country's leadership is furious with the Americans and Nato forces for last month's incident on the border in which 28 Pakistani troops were killed.
The absence of a Pakistani delegation from this week's Bonn conference was a powerful signal in its own right. It suggests that Pakistani anger with the US is so intense that it will not even indulge in the usual polite formalities of public diplomacy and speech making about the need for regional peace.
What this diplomatic snub, and the alleged complicity of the ISI with bombings by the Haqqani network, may add up to is a concerted attempt to make the exit of western forces from Afghanistan as humiliating as possible. Spectacular attacks, be they on Afghan government buildings, Nato convoys or the US embassy are all designed to add to the impression of a failed security campaign and a client government in Kabul that will totter as western troops pull out.
As for the stirring of sectarian tensions, this has precedents in Iraq where both Iran and Saudi Arabia were accused of fanning the flames of Shia/Sunni violence in order to create anarchy, embarrassing the Americans and undermining the Baghdad government at one and the same time.
The orgy of violence that resulted during 2005-2006 was only stemmed by the US troop surge, reversing earlier drawdown decisions, an exercise that the then Senator Obama opposed, and would be most unlikely to back in the case of Afghanistan.