Complex sentence: The Danish-Norwegian flotilla ambushed the Swedish fleet while it was positioned in the harbour of Dynekilen, overcome and destroyed a small island fort equipped with six 12-pounder guns positioned in the harbour entrance.
Split into simpler sentences: The Danish-Norwegian flotilla ambushed the Swedish fleet while it was positioned in the harbour of Dynekilen. In the process, it overcame and destroyed a small island fort equipped with six 12-pounder guns positioned in the harbour entrance.