During the Philippines campaign (1941–1942), when Japanese forces invaded the Philippines, Smith fled to Negros island where he and his Filipino friends were captured and taken in as a prisoner of war. For three years, Smith was then interned in various internment camps until he was ultimately relocated to Santo Tomas Internment Camp. The camp housed more than 4,000 internees from January 1942 until February 1945. At Santo Tomas, he continued to treat various prisoners and saved the lives of dozens of internees, many of which were starved.