The largest amount of casualties during the First World War were sustained when advancing on the enemy rather than in the comparative safety of the trenches. The trenches were not all that safe though. What proportion of Allied casualties on the Western Front occurred inside a trench?

Faced with a long war, the WW1 armies dug trenches in the muddy ground.  These trenches, dirty, cold and wet, were to be the temporary homes for millions of young men.