Fact File : Conscription Introduced
27 April 1939
Outcome: The British armed forces increased in number by more than 1.5 million by the end of the year conscription was introduced.
The Emergency Powers (Defence Act) of August 1938 had empowered the British government to take certain measures in defence of the nation and to maintain public order.
The Defence Act contained around 100 measures aimed at calling up military reservists and Air Raid Precautions (ARP) volunteers for mobilisation. It's estimated that about half a million people also volunteered to join the ARP, the Territorial Army (TA) and the RAF Volunteer Reserve. But volunteers were not enough.
The Military Training Act of 27 April 1939 responded to Hitler's threat of aggression in Europe. All British men aged 20 and 21 who were fit and able were required to take six months' military training. Even so, when war broke out the British Army could muster only 897,000 men, compared to France's five million.
Another act of parliament was necessary to increase the numbers. The National Service (Armed Forces) Act made all able men between the ages of 18 and 41 liable for conscription; as part of the legislation it was decided that single men would be called to war before married men.
Men aged 20 to 23 were required to register on 21 October 1939 - the start of a long and drawn-out process of registration by age group, which only saw 40-year-olds registering in June 1941.
By the end of 1939 more than 1.5 million men had been conscripted to join the British armed forces. Of those, just over 1.1 million went to the British Army and the rest were split between the Royal Navy and the RAF.
The fact files in this timeline were commissioned by the BBC in June 2003 and September 2005. Find out more about the authors who wrote them.