The outgoing British Armed Forces chief told ITV News it was "necessary" that the West would have to negotiate with the Taliban.
On the eve of his handover, General Sir David Richards acknowledged it was difficult to exchange words and bullets at the same time.
He told ITV News deputy political editor Chris Ship, "Every war through history has ended through a political process of some kind."
The general also defended the huge cuts in the defence budget he had to approve over the last two years.
He said: "We decided consciously, the Chiefs of Staff, that we had to play our part in putting the country back on the right footing.
"Clearly no one who is serving likes to see cuts to the armed forces, but they were a necessary evil."