Eight years ago the British Army arrived in Helmand in Afghanistan confident they could keep the peace, defeat the Taliban and rebuild the impoverished province. Now Britain's troops are leaving - 453 have given their lives. This two-part series tells the story of the conflict in Afghanistan and asks what has been achieved and whether, after such a bruising experience, the British have the will to fight in distant lands again.Part one examines the buildup to the conflict and reveals a story of misplaced hope and confused aims that quickly led to the very real threat of a catastrophic defeat.