On 23 May, Rhys-Davids gained his first victory, shooting an Albatros D.III fighter down out of control. On 24 May he scored three victories in an hour. One day later, he shot down another for his fifth victory and became a flying ace. The second to fifth victories were against enemy observer aircraft; Rhys-Davids repeated the tactics of diving and eliminating the gunner before bringing down the aircraft. In late May No. 56 Squadron moved to Saint-Omer. On 26 May he destroyed another Albatros followed by another on 4 and 7 June, the former date being the first day of the seven-day battle for Messines. On 5 June 1917, after his sixth triumph, he received a telegram informing him that along with Captain Cyril M. Crowe and Second Lieutenant Reginald Hoidge he had been awarded the Military Cross (MC). During the last battle Rhys-Davids's SE5, A4563, had its propeller damaged and its right top wing's main spar was shattered by ground fire.