Mixed messages over Afghanistan mission timetable?
US and British generals have always resisted setting timetables for their mission in Afghanistan.
In part because it's been impossible to predict the pace of progress - so far it has been much slower than anticipated.
But military commanders also fear that setting any date for a drawdown, or withdrawal, of troops will send a signal to the Taliban that there's a limit to how long they can stomach the fight.
Western politicians, however, are more acutely aware of the limit to their public's patience.
So senior officers on both sides of the Atlantic have had to accept the fact that their political masters want to set out some indications of how long this will take.
Until now David Cameron has been careful to stress that any dates for a drawdown of British forces will be dependent on conditions on the ground.
But in recent weeks timelines have become harder.
The prime minister has now made clear that British troops will end their combat role in Afghanistan by 2015.
With Mr Cameron's latest comments - that some British troops could start coming home by next year - that sense of unease among senior officers is likely to grow.
There is a feeling among some British military commanders that the government is now sending out mixed messages.
The prime minister says that an early exit of British troops will be dependent on the transition to Afghan forces.
But few in the British Army believe that those security forces will be ready by 2011.
Senior officers also feel that the longer they can "hold the line", the better the chances of success.
The prime minister still says British troops are there to get the job done. He denies there's been a change in policy.
But at the very least there is now a new emphasis on timelines.
British servicemen might well feel that such a shift will only make their job harder, and cheapen the sacrifices they've already made.