Complex sentence: After dark on 11 October, tapes were laid beyond the front line, for the troops to form up on beyond a possible German counter-barrage; to avoid detection, scouts patrolled further forward, ambushing German patrols.
Split into simpler sentences: After dark on 11 October, tape was laid beyond the front line, for the troops to form up on beyond a possible German counter-barrage. To avoid detection, scouts patrolled further forward, ambushing German patrols.