Imagine an enemy attacking everywhere but hard to spot. Imagine an enemy that can't be shot, will not surrender and keeps coming back. Worse still, imagine an enemy that has six legs and lives on human blood...
We are talking lice. 
Just half a centimetre long but one of the worst miseries of trench life for a soldier in the First World War.
April 1915. Time for the British Army to call in Captain Peacock! |