A reserved occupation is an occupation considered important enough to a country that those serving in such occupations are exempt—in fact forbidden—from military service. In a total war, such as the Second World War, where most fit men of military age were conscripted into the armed forces, exceptions were given to those who performed jobs vital to the country and the war effort which could not be abandoned or performed by others. Not only were such people exempt from being conscripted, they were often prohibited from enlisting on their own initiative, and were required to remain in their posts. Examples of reserved occupations include medical practitioners and police officers, but what is or is not a reserved occupation will depend on war needs and a country's particular circumstances.
In 1938, a Schedule of Reserved Occupations was created with the goal of exempting skilled workers from being conscripted into service. This idea was drawn up because of lessons learned during World War I when many skilled labourers were drawn into service, which created problems where positions needed filling. Examples of reserved occupations in the Second World War included coal mining, ship building, and many engineering-related trades. The idea was constantly reviewed throughout the war, as women, again, began to work more in industries such as munitions. This meant that men were free to join other organisations such as the Special Constabulary, the Home Guard or the ARP. It also allowed for men to join up and give them responsibilities towards the war effort, as well as allowing for them to be less stressed about not being able to directly be involved in the action. Also, many pacifists and conscientious objectors worked in reserved occupations as a compromise or to avoid call-up. Harper Adams Agricultural College saw a huge demand for places during the Second World War, as both agricultural students and farmers were exempt from conscription, as were students. In the UK, coal mining was not a reserved occupation at the start of the war, and there was a great shortage of coal miners. Consequently, starting in December 1943, one in ten men conscripted was chosen at random to work in the mines. These men became known as "Bevin Boys" after the creator of the scheme, Ernest Bevin, the Minister of Labour and National Service. A schedule of Reserved Occupations also existed in Canada during World War II.