Complex sentence: Key tracks from the battle 9 April 1940 (Operation Weserübung) is partially visible There have been military activity on Odderøya from 1667 until 1999, when the fortress was phased out.
Split into simpler sentences: Key tracks from the battle of 9 April 1940 (Operation Weserübung) are partially visible. There has been military activity on Odderøya from 1667 until 1999, when the fortress was phased out.