Why do people sacrifice their lives?

The Why Factor - A podcast by BBC World Service

Why do people give their lives for a nation? For a cause? As the world marks the centenary of the First World War, bereaved families reflect on the sacrifices made by their loved ones. What is the true nature of modern sacrifice? Presented by Mike Williams Produced by Ben Crighton(Photo: Poppies pegged on a wall bearing the names of soldiers who lost their lives in World War One. Credit: Philippe Huguen/AFP/GettyImages)