Complex sentence: At midnight a German counter-attack gradually pushed the French back into the communication trench, until a French artillery barrage was arranged and troops on the outskirts of Ablain advanced to the refinery along the stream, as the troops at the communication trench reorganised and attacked again.
Split into simpler sentences: At midnight a German counter-attack gradually pushed the French back into the communication trench. A French artillery barrage was arranged and troops on the outskirts of Ablain advanced to the refinery along the stream, as the troops at the communication trench reorganised and attacked again.