The Battle of Tannenberg Line (German: Die Schlacht um die Tannenbergstellung; Russian: Битва за линию «Танненберг») or the Battle of the Blue Hills (Estonian: Sinimägede lahing) was a military engagement between the German Army Detachment Narwa and the Soviet Leningrad Front. They fought for the strategically important Narva Isthmus from 25 July–10 August 1944. The battle was fought on the Eastern Front during World War II.