Complex sentence: After making landfall at Marseilles, the 5th Pioneers were transported overland by train to Hazebrouck, where they moved into a camp around Bae St Maur where they laid telephone cables and constructed railway lines, as part of their introduction to the front line.
Split into simpler sentences: After making landfall at Marseilles, the 5th Pioneers were transported overland by train to Hazebrouck, where they moved into a camp around Bae St Maur. There they laid telephone cables and constructed railway lines, as part of their introduction to the front line.