National Service (Armed Forces) Act 1939

The National Service (Armed Forces) Act 1939 was enacted immediately by the Parliament of the United Kingdom on the day the United Kingdom declared war on Germany on 3 September 1939, at the start of the Second World War. It superseded the Military Training Act 1939 passed in May that year, and enforced full conscription on all males between 18 and 41 resident in the UK. It was continued in a modified form in peacetime by the National Service Act 1948.

Exemptions
Only a few categories were exempted: Pregnant women were liable to be called up, but in practice were not.
 * British subjects from outside Britain and the Isle of Man who had lived in the country for less than two years
 * Students
 * Persons employed by the government of any country of the British Empire except the United Kingdom
 * Clergy of any denomination
 * Those who were blind or had mental disorders
 * Married women
 * Women who had one or more children 14 years old or younger living with them. This included their own children, legitimate or illegitimate, stepchildren, and adopted children, as long as the child was adopted before 18 December 1941.
 * Conscientious objectors
 * People working in reserved occupations