In February 1917 Robertson was attached to the Desert Column as a staff officer. From there, he was sent to staff school in Egypt. However, on 7 March he suffered a broken leg in a riding accident and was hospitalised for two months. He returned to the staff school in May and finally graduated on 17 June. He was then posted to the newly formed Yeomanry Mounted Division as a General Staff Officer (Grade 3). In March 1918, he was posted to Headquarters Delta Force in Cairo. This was disbanded in April and Robertson became Deputy Assistant Adjutant General (DAAG) at AIF Headquarters in Cairo. In January 1919, he became Assistant Adjutant General (AAG). He returned to Australia in July 1919. In addition to his Distinguished Service Order, he was twice mentioned in despatches, and awarded the Order of the Nile (4th Class) by the Sultan of Egypt.