Leading article: The more protracted the withdrawal, the costlier it will be Incidents such as yesterday's killing of three British servicemen in Helmand Province are, thankfully, still rare enough to make the headlines. But these shootings, where the gunman wears an Afghan uniform and is among those being trained by the British and others, are becoming more frequent, as preparations accelerate for the complete withdrawal of foreign combat troops by the end of 2014. President Obama's announcement of a deadline for the departure of US forces always risked giving comfort to the Taliban and others intent on violent resistance to outside intervention. Nor is it easy to identify a trainee soldier or policeman who may turn rogue. But the welcome for foreign troops, such as it was, has expired. With Australia, New Zealand and, most recently, France saying that their contingents within the international force will be leaving early, the argument grows ever stronger for the whole withdrawal to be completed as quickly as is practically possible.