Complex sentence: Having been advanced to KCB on 18 February 1915 and made a Grand Officer of the French Legion of Honour on 10 September 1915, he was promoted to lieutenant general on 28 October 1915 and then became Chief of the Imperial General Staff on 23 December 1915.
Split into simpler sentences: Having been advanced to KCB on 18 February 1915 he was made a Grand Officer of the French Legion of Honour on 10 September 1915 and promoted to lieutenant general on 28 October 1915. He became Chief of the Imperial General Staff on 23 December 1915.