The Jolly Roger is the default symbol of pirates and piracy. During World War I however, some British submarine crews began flying the Jolly Roger to indicate a successful patrol. This was somewhat problematic because World War I was also a war of propaganda. British propaganda was trying to convince the world that Germany was the predator and that the British were the guardians of civilization. British submarines flying the pirate flag risked upsetting this narrative. Nevertheless, British submarines continued the practice. More than a hundred years later, the tradition continues and has been adopted by navies around the world.