Complex sentence: The existing positions were consolidated and Headlam returned to divisional headquarters by and obtained two battalions from the reserve brigade, which struggled through congested trenches and eventually took over the right of the 63rd Brigade and left of the 64th Brigade.
Split into simpler sentences: The existing positions were consolidated and Headlam returned to divisional headquarters by and obtained two battalions from the reserve brigade. The reinforcements struggled through congested trenches and eventually took over the right of the 63rd Brigade and left of the 64th Brigade.