Complex sentence: The Russian Second Pacific Squadron (the renamed Baltic Fleet) sailed 18,000 nautical miles (33,000 km) to relieve Port Arthur only to hear the demoralizing news that Port Arthur had fallen reached the fleet while it was still at Madagascar.
Split into simpler sentences: The Russian Second Pacific Squadron (the renamed Baltic Fleet) sailed 18,000 nautical miles (33,000 km) to relieve Port Arthur. The demoralizing news that Port Arthur had fallen reached the fleet while it was still at Madagascar.