British soldiers may have to fight in Afghanistan for three generations, the general taking over as head of the Army has said.
He said: "A whole generation, or two, or maybe even three of our soldiers - their professional lives will be dominated by this campaign."
Although military and political leaders have long stressed that the campaign to combat insurgents in Afghanistan would be a long haul, it is the first time a senior commander has put a detailed time scale on the operation.
Aides of Sir David stressed that for the Army a generation meant about four years, the average time a young infantryman will serve on the front line in his career.
By that measure, Britain's military involvement could continue until at least 2021.
Currently Commander in Chief, Land Forces, Sir David will take over next month from Sir Richard Dannett.
Previously he served for a year as commander of ISAF, the international force in Afghanistan.