Complex sentence: House-to-house fighting was going on in Souchez and in the 16th Division area the front line for had been lost and some French troops had reached German artillery positions, beyond which were no trenches.
Split into simpler sentences: House-to-house fighting was going on in Souchez and in the 16th Division area, the front line for had been lost. Some French troops reached German artillery positions, beyond which were no trenches.