Complex sentence: The naval Battle of Oliwa or Battle of Gdańsk Roadstead took place on 28 November 1627 during the Polish-Swedish War outside Gdańsk harbour, but it is commonly known as the Battle of Oliwa (Oliwa is now a part of Gdańsk).
Split into simpler sentences: The naval Battle of Oliwa or Battle of Gdańsk Roadstead took place on 28 November 1627 during the Polish-Swedish War outside Danzig (Gdańsk) harbour. It is commonly known as the Battle of Oliva, (Polish: Oliwa, Oliwa is now a part of Gdańsk).