this is bbc news with me christian fraser. in the last half—hour, joe biden has spoken about the us's withdrawal from afghanistan after 20 years of war. the us president paid tribute to american military for their service in afghanistan, but made clear what he believes us foreign policy now needs to change. this is a new world. the terror threat has metastasized well away from afghanistan. in kabul, american uniforms, american weapons, but now worn by the taliban — the spoils of a war that was the us's longest military mission. now it has ended in the worst of ways, and it will live long in memory, here in afghanistan, in america and far beyond.