<P> A convention passed in November 1887 came to the aid of fishermen of the North Sea . This law restricted liquor traffic from bum boats . The island of Heligoland was ceded to Germany 1890 when the United Kingdom and Germany signed the Treaty of Heligoland . The Cod War of 1893 erupted between Denmark and Britain over fishing territories . Denmark declared a fishing territory of 13 nautical miles (24 km) around their shores which included Iceland and the Faroe Islands . Britain did not acknowledge this claim . </P> <P> Tensions in the North Sea were again heightened in 1904 by the Dogger Bank incident, in which Russian naval vessels mistook British fishing boats for Japanese ships and fired on them, and then upon each other . The incident, combined with Britain's alliance with Japan and the Russo - Japanese War led to an intense diplomatic crisis . The crisis was defused when Russia was defeated by the Japanese and agreed to pay compensation to the fishermen . </P> <Table> <Tr> <Th_colspan="2"> <Ul> <Li> </Li> <Li> </Li> <Li> </Li> </Ul> North Sea 1914--1918 </Th> </Tr> <Tr> <Td_colspan="2"> <Ul> <Li> U-Boat Campaign </Li> <Li> 1st Heligoland Bight </Li> <Li> 22 September 1914 </Li> <Li> Texel </Li> <Li> 1st Yarmouth </Li> <Li> Scarborough </Li> <Li> Cuxhaven </Li> <Li> Dogger Bank </Li> <Li> Noordhinder Bank </Li> <Li> 2nd Dogger Bank </Li> <Li> 29 February 1916 </Li> <Li> 2nd Yarmouth </Li> <Li> Jutland </Li> <Li> 19 August 1916 </Li> <Li> 1st Dover Strait </Li> <Li> 16 March 1917 </Li> <Li> 2nd Dover Strait </Li> <Li> 4 May 1917 </Li> <Li> Lerwick </Li> <Li> 2nd Heligoland Bight </Li> <Li> Zeebrugge </Li> <Li> 1st Ostend </Li> <Li> 2nd Ostend </Li> <Li> Mine Barrage </Li> <Li> Tondern </Li> <Li> 24 October 1918 </Li> </Ul> </Td> </Tr> </Table> <Tr> <Th_colspan="2"> <Ul> <Li> </Li> <Li> </Li> <Li> </Li> </Ul> North Sea 1914--1918 </Th> </Tr>

When did the german ocean become the north sea