During World War One, submarines began to be used widely for the first time. German submarines called U-boats tried to cut off Britain’s sea routes to starve it into submission. Alex Last presents archive recordings of the German and British submariners who risked their lives fighting in the new undersea weapon 100 years ago.Photo: Two German submarines, the U35 and U42, surface off the Mediterranean coast. (Photo by General Photographic Agency/Getty Images)