The murders of 16 civilians by a US serviceman were the latest in a chain of extremely violent incidents coming at a fraught time for the Afghan mission, and when there is again rising tension between President Hamid Karzai and his Western sponsors. The two recent episodes – the burning of Korans by US officials at Bagram airbase last month and yesterday's killings in Kandahar – could not have been foreseen. One was an act of stupidity and the other the work of someone apparently deranged.

But they are an immense propaganda boost to the insurgents and add to the alienation of the population, many of whom are susceptible to conspiracy theories of foreign forces secretly engineering these treacherous acts. The outbreak of strife which followed the Koran burnings, with Afghan soldiers turning their guns on their Western allies, illustrated the ferocity of this conviction.

President Karzai is viewed by Western officials as doing little to calm feelings. Yesterday he described the shootings in Kandahar by the lone soldier as "intentional murders by US forces". At the same time he wants to ban night operations against the Taliban, seen as vital by US and UK commanders.

Last week also saw the deaths of six British soldiers, the most killed in one attack in the war, in an area that had supposedly been cleared. There have been other high fatalities in single incidents. Five members of the forces were blown up in Sangin and five more killed by an Afghan policeman at Nad-e-Ali. But these were in 2009, when territory was being wrested back from the Taliban. Deaths now are in a mission which will soon rapidly start winding down as the West rushes for the exit door in 2014.

The Government's position remains that the troops are there to prevent bombs going off in the streets of the UK. The fact remains that the vast majority of terrorist plots uncovered in this country are connected to Pakistan, not Afghanistan. There is a case for arguing one needs forces in Afghanistan to prevent it returning to ungoverned space and a terrorist training ground. But this has less credence when the US and UK are not just scrambling to get out, but keen to hold talks with the Taliban about their role in the country's future. Meanwhile, the recent deaths in Afghanistan are used for the expediencies of realpolitik. After French troops were killed by their Afghan comrades, Nicolas Sarkozy threatened to pull his forces out immediately. This, however, was for home consumption with elections coming up. Karzai, too, has sought to use what has happened for his own purposes. There is widespread suspicion in Afghanistan that the President wants to run for a third term; being seen to be standing up to the West, his supporters believe, will do him no harm.