Complex sentence: The cavalry phase of the Battle of Sharon began as soon as the gap was made during the infantry attacks, when the 5th Cavalry Division led the way north up the Plain of Sharon followed by the 4th Cavalry Division with the Australian Mounted Division in reserve.
Split into simpler sentences: The cavalry phase of the Battle of Sharon began as soon as the gap was made during the infantry attacks. The 5th Cavalry Division led the way north up along the Plain of Sharon followed by the 4th Cavalry Division with the Australian Mounted Division in reserve.