'We risk our lives...', First World War poster, 1917, (c1920). Artist: James Prinsep Beadle [Getty Images]

'We risk our lives...', First World War poster, 1917, (c1920). 'A Message from our Seamen: We risk our lives to bring you food. It's up to you not to waste it.' Illustration from The Illustrated War Record of the Most Notable Episodes in the Great European War 1914-1918, seventh edition, (The Swarthmore Press Ltd, London, c1920). (Photo by The Print Collector/Print Collector/Getty Images)

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