At the outbreak of war in 1914 Sir Ronald Ross had attained the rank of Lieutenant-Colonel in the Territorial Force (which he had entered in July 1908 as a Major in the Medical Service) and it was with this rank that he was appointed Consulting Physician in Tropical Diseases to the Hospitals for Indian Troops in England on 21st December 1914. During the year 1916 the War Office was becoming increasingly concerned about the prevalence of malaria amongst troops returning to England and it was decided to open special malarial hospitals in all eight British Commands. Three Consultants in Malaria, Ross being one of them, were appointed from 15th February 1917, to take overall charge of these hospitals. Ross remained at the War Office until 17th September 1919, having been promoted to Colonel on 5th February 1918, when he was demobilised and appointed Honorary Consultant in Malaria to the Ministry of Pensions.
During his period of service with the War Office Ross made visits of inspection and acted as adviser to the four Commands under his control in the South of England as well as visiting France, Alexandria, Salonika and the Dardanelles. In addition to his responsibility for the control and eradication of malaria in the Commands and amongst the troops abroad Ross directed malaria research at the Fourth London General Hospital.
Until his appointment with the War Office Ross had been more concerned with the etiology and prevention of malaria than with its treatment with the result that he was now obliged to familiarise himself with the most effective methods of treatment. In a letter to Surgeon-General Gorgas on 22nd April 1917 Ross writes ‘I write to you with permission to ask for information regarding the best standardised method of treating malaria.’. (WO1/1/121). Ross stated in his Memoirs ‘It was the first time that I had been employed on executive work connected with my own subject; but it came too late.’. (p. 519). He was aged 60 when he was appointed Consultant in Malaria after having spent twenty years trying to educate public health authorities all over the world that prevention of malaria was infinitely preferable to treatment of the disease. Now that he had the opportunity to do the work required with little or no opposition he found that it was too late in the day.
Ross was demobilised on 17th September 1919 but was simultaneously given the appointment of Honorary Consultant in Malaria to the Ministry of Pensions.