Wackett later transferred to No. 3 Squadron AFC in France and played a significant role in the Battle of Hamel fought on 4 July 1918. Captured German documents revealed that they had been experimenting with dropping ammunition from aircraft and No. 3 Squadron was asked to investigate doing the same. Wackett was asked to do the work as his reputation had spread; 'he had a gift for mechanical inventions' according to his superiors. Now a captain, he devised a small parachute that could be used to drop supplies to troops, designed a modified bomb rack to hold the supplies and then trained No. 3 Squadron personnel in the required technique. General Monash's battle plan for Hamel involved resupplying the engaged machine-gunners with ammunition dropped by aircraft. In the event No. 3 Squadron was assigned other tasks during the battle and the ammunition dropping was performed by No. 9 Squadron RAF. Monash later wrote, "at least 100,000 rounds of ammunition were during the battle with obvious economy in lives and wounds. The method thus initiated became general in later months". Later that year, on 25 September, Wackett undertook a daring reconnaissance mission in 3 Squadron's first Bristol F.2 Fighter, when he penetrated six miles (10 km) behind enemy lines to take aerial photographs of the German Joncourt-Villers Outreaux line, that were needed for a forthcoming attack. Two days later he carried out an ammunition resupply flight to some isolated troops using the equipment he had designed. As a result of these two actions he was awarded the Distinguished Flying Cross. By the end of the war two months later he had been promoted to the rank of major. On 6 January 1919 he was appointed the Commanding Officer of No. 7 Squadron AFC based at Leighterton in England. 7 Sqn. had acted as the training unit for No. 3 Squadron during the recent conflict and Wackett remained the CO until the Squadron was disbanded in March that year, at which time he returned to Australia.