Smith was a Welsh major in the British military during World War II. He received his training in the British Life Guard, Black Watch, and before the war had studied at the University of Heidelberg in Germany. He was bilingual, and spoke both English and German. During the war, he was employed by MI6 was a secret agent. Under the alias Johann Schmidt, he pretended to be of German birth, and spent several years undercover as an SS officer where he befriended Colonel Wilhelm Wilner. In this capacity, he fed Wilner useless and out of date information.