The 10th Light Horse was reorganised after returning to Egypt in January 1916, and Robertson assumed command of B Squadron, with the AIF rank of major from May 1916. This was as far as he could go, for Duntroon graduates could not be promoted above major in the AIF. This was the result of an AIF policy aimed at giving them a broad a range of experience, which would benefit the post-war Army, while not allowing an accumulation of young officers of high rank, for whom the reduced post-War Army would not have sufficient posts. His substantive rank remained that of lieutenant; he would not be promoted to the substantive rank of captain in the PMF until 30 September 1920, and promotion to major would not come until 1 July 1932. At the Battle of Magdhaba, his colonel was wounded and Robertson took over command of the 10th Light Horse. He was awarded the Distinguished Service Order (DSO) for his actions during this battle. His citation read: