In the Second World War, trauma care improved alongside advances in medicine:
the discovery of penicillin in 1929 reduced complications from wound infections
emergency transport systems during conflict continued to improve, this decreased transport times and improved mortality rates .
hypovolemic shock was better understood in the 1930’s due to work by Blalock  and these principles were implemented by physicians during WW II.
the management of pneumothorax, hemothorax and penetrating chest trauma improved due to the sheer volume of cases, this resulted in decreased mortality.
3. Molner, T.F. (2004). "Changing Dogmas: History of Development in Treatment Modalities of Traumatic Pneumotorax, Hemothorax, and Posttraumatic Empyema Thoracis." Annals of Thoracic Surgery 77:372-8.