The National Service (Armed Forces) Act 1939 was enacted by the Parliament of the United Kingdom on 3 September 1939, the day the United Kingdom declared war on Germany at the start of the Second World War. It superseded the Military Training Act 1939 (enacted in May of that year) and enforced full conscription on all male British subjects between 18 and 41 who were present in Great Britain, subject to certain exemptions. By a royal declaration in January 1941, the term Great Britain was extended to include the Isle of Man.