It was not, perhaps, entirely surprising that insurgents would want to demonstrate the scope and reach of their power by carrying out lethal strikes the day after the international great and the good were meeting in Bonn to chart Afghanistan's future.
The attacks showed the relative impotence of the West in Afghanistan when faced with determined terrorists, and the scale of the slaughter was shocking. But what makes this a matter of deep concern is that the Shia community was specifically targeted – the first time such sectarian killings had taken place in a decade of the insurgency, bringing the prospect of another front line opening up in the conflict.
The country's largest Shia population, the Hazaras, have suffered massacres in the hands of the Sunni Taliban during the civil war. The Taliban had argued that the casualties were not due to sectarianism, but because the Hazaras were supporting the Northern Alliance against Mullah Omar's regime. No such excuse can be offered for yesterday's carnage, with the victims in Kabul, Mazar-i-Sharif and Kandahar commemorating Ashura, one of the most holy days in the Shia religious calendar.
So who was responsible? The Taliban were quick to deny it was them, condemning the "inhuman acts", and there is nothing to suggest their involvement. A recent study of the movement did note, however, a growth of communal and tribal tension and put the blame (apart from the standard castigation of the US) on two of the country's neighbours, patently Sunni Pakistan and Shia Iran.
Some have already made up their minds about where the guilt lies. When the news of the attack broke in Bonn yesterday morning, a member of the Afghan delegation to the conference declared bitterly: "Another gift from our Pakistani neighbours."
There seems to be no logical reason why Pakistan and Iran should start a proxy religious war. Sectarian bombings and shootings are, however, rife in Pakistan with Sunni militants, including the Pakistani Taliban, carrying out repeated attacks on Shias. Al Qa'ida, headquartered in Pakistan, have also been involved in attacks and it was al-Qa'ida in Mesopotamia, led by Abu Musab al-Zarqawi, which started the bloodiest Muslim sectarian war in recent times, in Iraq.
The savage strife in Iraq between Sunnis and Shias resulted in the US-led coalition forces getting a respite of sorts, so focused were the two factions on killing each other. Yesterday's bombings do not mean that Afghanistan will necessarily go the way of Iraq and British and American troops will face less danger. But the introduction of such an incendiary factor in an already brutal conflict will be met with grave foreboding by a population already battered by years of relentless violence.