Sean Smith in Afghanistan

Medevac troops look out from their Pavehawk helicopter while heading to pick up casualties Photograph: Sean Smith for the Guardian

Troops evacuate a wounded Afghan civilian truck driver onto a helicopter in Kandahar. The victim was part of a military convoy hit by an IED Photograph: Sean Smith for the Guardian

Medevac troops with the wounded Afghan truck driver Photograph: Sean Smith for the Guardian

Troops look out from their helicopter while heading to pick up casualties in Kandahar Photograph: Sean Smith for the Guardian

Canadian and Medevac troops evacuate a mortally wounded soldier after the victim's vehicle was hit by an IED in Kandahar Photograph: Sean Smith for the Guardian

A staff sergeant onboard a helicopter Photograph: Sean Smith for the Guardian

US marines take cover as they come under fire during a firefight in Garmsir, southern Helmand Photograph: Sean Smith for the Guardian

Marines regroup after a firefight while on patrol Photograph: Sean Smith for the Guardian

Marines in Garmsir, southern Helmand Photograph: Sean Smith for the Guardian

A dusty marine at Patrol Base Karma in Garmsir after a patrol Photograph: Sean Smith for the Guardian

US troops and Afghan police from Dand district command centre on an early morning patrol through a pomegranate orchard in Kandahar Photograph: Sean Smith for the Guardian

US and Canadian troops and Afghan police rest during a patrol Photograph: Sean Smith for the Guardian

An American soldier photographs a man arrested outside the Dand district command centre by Afghan police. The containers recovered from his vehicle were believed to contain explosives used for making IEDs Photograph: Sean Smith for the Guardian