Complex sentence: A raider had the tactical advantage in deciding when to open fire, before it was unmasked and investigating ships courted danger, if they approached from a direction favourable to the raider's guns and torpedoes.
Split into simpler sentences: A raider had the tactical advantage in deciding when to open fire before it was unmasked. Investigating ships courted danger if they approached from a direction favourable to the raider's guns and torpedoes.