Complex sentence: The Germans had still hoped to smash the 6th Army between 6 and 8 September, but the 6th Army was reinforced on the night of 7/8 September by reserve infantry ferried from Paris.
Split into simpler sentences: The Germans had still hoped to smash the Sixth Army between 6 and 8 September. But the Sixth Army was reinforced on the night of 7/8 September by reserve infantry ferried from Paris.