Both North and South Korea, which are still technically at war with each other, require citizens to complete some form of national service.
In the South, male citizens must complete between 21 and 24 months of military service but exemptions are given to certain top athletes – such as those who win Olympic medals.
North Korea has the longest military service in the world with men spending 11 years in the military and women seven.
In Syria, military service is compulsory for all men and Amnesty International says that those who avoid it have been jailed for 15 years.
Concerned by Russia’s military drills in the Baltic, Sweden reintroduced military conscription in 2017, having abolished it in 2010. In the Swedish system, “men and women are treated equally".
In Russia, all men between the ages of 18 and 27 must spend a year in the military.
In Finland, men are asked to serve up to 347 days, after which they are transferred into the reserves.
Lithuania brought back conscription in 2016, having abolished it in 2008.
In Greece, men over the age of 19 are eligible for nine months of compulsory military service, whilst in Switzerland, men must complete 21 weeks of training, with attendance at additional training camps expected annually.
Moldova also expects men to complete one year of compulsory service.
In Israel, both men and women are required to serve between two and three years in the Israeli Defence Forces.
In Iran, men are obliged to spend 18 months completing military service.
Whilst in Singapore, men must complete two years of military training between the ages of 18 and 21.
A brief history of conscription
Pre-First World War Britain relied on an entirely volunteer Armed Forces. Neighbouring European powers like France and Germany forced men into service.
The First World War changed Britain's approach and in 1916 the Military Service Act was passed.
All single men in Great Britain between 18 and 41 were eligible, with exemptions included for certain professions such as clergymen. A second Act in May that year extended it to married men.
The Government considered extending the Act to Ireland but, given public opinion in the wake of the Easter Rising, decided not to.
After the First World War the act was extended only until 1920. That changed in 1939 when war broke out with Germany. Britain imposed conscription on men between 18 and 41. In 1941 it widened the eligibility to include women for the first time.
Post war more than two million British men were conscripted into the Armed Forces, serving in places like Korea and Malaya. That ended in 1963.
Conscription during times of war has a longer history in the United States and it has often been controversial. Its use during the Civil War caused a four-day long riot in 1863 in New York City.
Public opinion turned against “the draft” during the Vietnam War. One aspect of that was a widely perceived bias in deferments in favour of the rich.
The late US Senator John McCain, who served during the conflict, said:
"One aspect of the conflict, by the way, that I will never ever countenance is that we drafted the lowest-income level of America, and the highest-income level found a doctor that would say that they had a bone spur."
The remark was seen as a pointed dig at President Trump who was diagnosed in 1968 with a bone spur and received a medical deferment.
The draft lapsed in 1973 but the US Government “maintains the ability to reinstate it in case of a national emergency”.