At the outbreak of the First World War he was appointed as consultant neurologist to the British Expeditionary Forces. Working in a field hospital he had a unique opportunity for the investigation of the effects of lesions in specific regions of the brain on balance, vision and bladder function. While in France, Holmes met his future wife, Dr Rosalie Jobson, an Oxford graduate and an international sportswoman, to whom he subsequently proposed marriage while rowing on the Thames. His wartime observations on gunshot wounds re-awakened his interest in cerebellar disease which led to his classical analysis of the symptoms of cerebellar lesions described in his Croonian Lectures to the Royal College of Physicians in 1922.