Antony Beevor's Stalingrad, published by Penguin in 1998, was a worldwide bestseller, telling one of the most harrowing stories of the Second World War and reminding everybody of the power of narrative history in the hands of an expert storyteller. In this extract Beevor takes us back to December 1942 when the German 6th Army was surrounded by the Russians and facing annihilation. Only thoughts of Christmas kept German soldiers' hopes alive.