The deaths in Nad-e-Ali are extremely distressing and it is, of course, very worrying that they were carried out by an Afghan policeman. There will be a temptation now, if we are getting attacked by people supposedly from our own side, to say "Let's wash our hands of it".
However, the plain fact is that the only viable exit strategy involves preparing the Afghan security forces for taking over from us. We should only be there until this is done and then we must leave the Afghan forces to look after security in their own country.
This does not mean that we turn a blind eye to what are obviously deep problems within the Afghan forces, and the police in particular. Their training from the past leaves a lot to be desired and there are reports that they are poorly paid and sometimes infrequently paid. This is down to corruption – something Afghanistan suffers greatly from and something the international community must sort out.
In the past there has been a tendency to rush through the training process very quickly to get enough boots on the ground. This is counterproductive and self-defeating. There have been suggestions that any new deployment of Nato troops to Afghanistan must contain an adequate proportion of trainers – a sensible idea. Training should be given absolute priority.
The British forces carrying out the mentoring of Afghans are doing a very good job with great dedication. What happened in Nad-e-Ali must seem like a terrible betrayal. However, difficult as it is, they have to carry on. We do not have an indefinite timeframe in Afghanistan and patience will wear thin unless tangible progress is made. But this is not Iraq, and there are good, valid reasons for the West to have a presence in the country. For the time being, we need to carry on.
What we have seen in the fallout from the election is the great need for reform in Afghanistan, the need to root out malpractice. That applies not just to the political framework but the military one as well. We should help the Afghan people protect themselves against the Taliban, but they, in turn, must know that there needs to be a return for the investment we are making in troops and material. That return is a willingness to embrace reform.
Major-General Julian Thompson is the former commander of the Royal Marines