Rhyme accompanying the caricature:'Higgledy-piggledy, my black hun!She lays mines where the trade ships run;Friends and foes she treats as one –Higgledy-piggledy, my black hun!'
In February 1915 Germany declared the waters surrounding British Isles to be a war zone in which ships could be sunk without warning, and began the first U-Boat campaign with unrestricted attacks against merchant and passenger ships.
The British Navy retaliated in March by imposing a total sea blockade on Germany, prohibiting all shipping imports including food.
Gallery: Remembering the First World War: Home Front