 In February 1938 he was sent to Scotland where he became adjutant to the regiment's 4th Battalion, a Territorial Army unit serving as part of the 51st (Highland) Division, then commanded by Major General Victor Fortune.Still adjutant upon the outbreak of World War II in September 1939, Lang was sent to France, along with the rest of the 51st Division, in January 1940, where it formed part of the British Expeditionary Force (BEF).However, Lang became a prisoner of war in June after the German Army invaded France.