In April 1939, realizing that war was inevitable, he abandoned his art studies to enlist in the Royal Engineers. In January 1942, he was stationed in Singapore. After a month of fighting in Malaya, he was taken prisoner along with his cousin Tom Fordham Searle, when Singapore fell to the Japanese. He spent the rest of the war as prisoner, first in Changi Prison and then in the Kwai jungle, working on the Siam-Burma Death Railway. Searle contracted both beriberi and malaria during his incarceration, which included numerous beatings, and his weight dropped to less than 40 kilograms. He was liberated in late 1945 with the final defeat of the Japanese. After the war, he served as a courtroom artist at the Nuremberg trials and later the Adolf Eichmann trial (1961).