The news that six UK soldiers had been killed in Afghanistan was met by duly respectful and stoical tributes yesterday, first in Downing Street, then at the Ministry of Defence, and then in Parliament during Prime Minister's Questions. The Defence Secretary, Philip Hammond, insisted that what had happened would "not shake our resolve to see through the mission". David Cameron stressed the commitment of the troops to "getting the job done", while offering "everypossible support" to a political settlement.

In other words, the date for UK troops to be withdrawn remains the end of 2014. It will not be put back – though that would be the logical response to the failure of Afghan troops to ensure security, if the objective is still to leave behind a stable country. Nor will the withdrawal be brought forward – which might be interpreted as a forced retreat unless the security situation improves radically.

And if a wider perspective is taken, it can reasonably be argued that no change in either the policy or the timetable is called for. While the UK intervention in Afghanistan has been costly – in lives, as in money – when it is judged against past wars, the cost could have been much higher. Add the complexities of the terrain, early tactical mis-steps, and the circumstances in which the intervention began – the attacks of 9/11 and the overthrow of Afghanistan's Taliban regime – and it might be seen as remarkable that it is only with these six deaths that UK losses, over 10 years, have passed 400.

Of course, for those who remain unconvinced either by the rationale for going into Afghanistan at all or by the attainability of the objective, that is 400 too many – as it will be for many relatives and friends of the dead. There have also been times, though this is not one of them, when inadequate equipment as much as enemy action shared the blame: the six soldiers killed this week were travelling in one of most robust vehicles available.

With the date for withdrawal almost three years away, however, these fatalities cannot be seen in isolation. And it is hard to escape the impression that, even as the training of Afghan soldiers and police continues, little is changing so far as the authority of the government, overall security and the safety of foreign troops are concerned. In some ways, the situation appears to be deteriorating. More incidents seem to be reported in which newly trained Afghan troops and police directly attack their foreign allies or infiltrate supposedly secure buildings.

That US troops had disposed of copies of the Koran as rubbish was always going to be an incendiary revelation. But the violent protests that followed, and the speed with which they spread, exposed the knife-edge on which Afghanistan's security and that of the foreign troops is poised. With poppy-growing on the rise again, and the increase in the number of girls going to school likely to be reversed by the clerical rules on the subordinate position of women that President Karzai has just endorsed, the prospects for US and British troops to leave Afghanistan a significantly better place look markedly worse than they did even a year ago.

It has been argued that Mr Karzai's stance, notably on the position of women, can be explained by his government's recently acknowledged need to treat with the Taliban. But that is scant consolation. If to this and the other reversals is added the partial return of the Taliban as a precondition for stability, then the sense in keeping British troops in Afghanistan is unclear. President Obama was fortunate that the US was able to withdraw from Iraq in good order – not so the British from Basra. But the regrettable conclusion must be that the 2014 deadline for leaving Afghanistan leaves space for needless aggravation and killings. The withdrawal needs to be accelerated.