In December 1915, after he had recovered, Wavell was returned to General HQ in France as a GSO2. He was promoted to the substantive rank of major on 8 May 1916. In October 1916 Wavell was graded General Staff Officer Grade 1 (GSO1) as an acting lieutenant colonel, and was then assigned as a liaison officer to the Russian Army in the Caucasus. In June 1917, he was promoted to brevet lieutenant colonel and continued to work as a staff officer (GSO1), as liaison officer with the Egyptian Expeditionary Force headquarters.