How photographs told the story of

the Vietnam War

Historians argue over exactly when the Vietnam War started - but in the

United States, events to mark some of the conflict's 50th anniversaries

have begun.

In a new 50th anniversary book - Vietnam, The Real War - the US news agency Associated Press has chosen some of its most powerful images, taken by photographers embedded with US troops fighting the Communist Viet Cong.

David Willey - who covered the American military build up in South Vietnam for the BBC between 1965 and 1968 - has been speaking to former AP chief picture editor Hal Buell. Hear their thoughts on the conflict as they looked at some of the most memorable and striking images from the time.