Complex sentence: His corps took part in the Battle of Loos in September 1915, where he oversaw another 8,000 casualties on the second day, although his divisions were in reserve under the direct control of GHQ on that occasion.
Split into simpler sentences: His corps took part in the Battle of Loos in September 1915. Robbins 2005, p74 In the event he oversaw another 8,000 casualties on the second day, although his divisions were in reserve under the direct control of GHQ on that occasion.