Complex sentence: The 9th Division provided the coastal defence, from Cape Helles north to Bulair, where the 7th Division took over, while the 19th Division at Maidos was the corps reserve.
Split into simpler sentences: The 9th Division provided the coastal defence, from Cape Helles north to Bulair. Where the 7th Division took over, while the 19th Division at Maidos was the corps reserve.