1940年，醫院被改為軍方醫院。1941年日本侵港期間，山頂被炸彈轟炸，火勢蔓延至明德醫院。其後醫護人員及病人被拘留喺赤柱集中營，當時醫院主席Sir Vandeleur為監獄病人提供藥物而被拷打至死。1951年，醫院重新開放並將服務開放畀所有病人。
In 1940, the hospital was converted into a military hospital. During the Japan invasion of Hong Kong in 1941, the summit was bombed and the fire spread to Matoku Hospital. Subsequently, medical staff and patients were detained in Stanley concentration camp, where the then chairman of the hospital, Sir Vandeleur, was tortured to death while providing medicine to prison patients. In 1951, the hospital reopened and opened its services to all patients.