Conscription
In Morocco, the Berber looked south rather than north. The Moroccan Sultan Moulay Ismail, called "the Bloodthirsty" (1672–1727), employed a corps of 150,000 black slaves, called his Black Guard. He used them to coerce the country into submission.

In modern times: Modern conscription, the massed military enlistment of national citizens (levée en masse), was devised during the French Revolution, to enable the Republic to defend itself from the attacks of European monarchies. Deputy Jean-Baptiste Jourdan gave its name to the 5 September 1798 Act, whose first article stated: "Any Frenchman is a soldier and owes himself to the defense of the nation." It enabled the creation of the Grande Armée, what Napoleon Bonaparte called "the nation in arms", which overwhelmed European professional armies that often numbered only into the low tens of thousands. More than 2.6 million men were inducted into the French military in this way between the years 1800 and 1813.
The defeat of the Prussian Army in particular shocked the Prussian establishment, which had believed it was invincible after the victories of Frederick the Great. The Prussians were used to relying on superior organization and tactical factors such as order of battle to focus superior troops against inferior ones. Given approximately equivalent forces, as was generally the case with professional armies, these factors showed considerable importance. However, they became considerably less important when the Prussian armies faced Napoleon's forces that outnumbered their own in some cases by more than ten to one. Scharnhorst advocated adopting the levée en masse, the military conscription used by France. The Krümpersystem was the beginning of short-term compulsory service in Prussia, as opposed to the long-term conscription previously used.

In the Russian Empire, the military service time "owed" by serfs was 25 years at the beginning of the 19th century. In 1834 it was decreased to 20 years. The recruits were to be not younger than 17 and not older than 35. In 1874 Russia introduced universal conscription in the modern pattern, an innovation only made possible by the abolition of serfdom in 1861. New military law decreed that all male Russian subjects, when they reached the age of 20, were eligible to serve in the military for six years.
In the decades prior to World War I universal conscription along broadly Prussian lines became the norm for European armies, and those modeled on them. By 1914 the only substantial armies still completely dependent on voluntary enlistment were those of Britain and the United States. Some colonial powers such as France reserved their conscript armies for home service while maintaining professional units for overseas duties.

World Wars: The range of eligible ages for conscripting was expanded to meet national demand during the World Wars.
In the United States, the Selective Service System drafted men for World War I initially in an age range from 21 to 30 but expanded its eligibility in 1918 to an age range of 18 to 45. In the case of a widespread mobilization of forces where service includes homefront defense, ages of conscripts may range much higher, with the oldest conscripts serving in roles requiring lesser mobility.
Expanded-age conscription was common during the Second World War: in Britain, it was commonly known as "call-up" and extended to age 51. Nazi Germany termed it Volkssturm ("People's Storm") and included boys as young as 16 and men as old as 60. During the Second World War, both Britain and the Soviet Union conscripted women. The United States was on the verge of drafting women into the Nurse Corps because it anticipated it would need the extra personnel for its planned invasion of Japan. However, the Japanese surrendered and the idea was abandoned.

During the Great Patriotic War, the Red Army conscripted nearly 30 million men.

Arguments against conscription: 

Sexism: Men's rights activists, feminists, and opponents of discrimination against men: 102  have criticized military conscription, or compulsory military service, as sexist. The National Coalition for Men, a men's rights group, sued the US Selective Service System in 2019, leading to it being declared unconstitutional by a US Federal Judge. The federal district judge's opinion was unanimously overturned on appeal to the U.S. Court of Appeals for the 5th Circuit. In September 2021, the House of Representatives passed the annual Defense Authorization Act, which included an amendment that states that "all Americans between the ages of 18 and 25 must register for selective service." This amendment omitted the word "male", which would have extended a potential draft to women; however, the amendment was removed before the National Defense Authorization Act was passed.
Feminists have argued, first,  that military conscription is sexist because wars serve the interests of what they view as the patriarchy; second, that the military is a sexist institution and that conscripts are therefore indoctrinated into sexism; and third, that conscription of men normalizes violence by men as socially acceptable. Feminists have been organizers and participants in resistance to conscription in several countries.
Conscription has also been criticized on the ground that, historically, only men have been subjected to conscription. Men who opt out or are deemed unfit for military service must often perform alternative service, such as Zivildienst in Austria, Germany and Switzerland, or pay extra taxes, whereas women do not have these obligations. In the US, men who do not register with the Selective Service cannot apply for citizenship, receive federal financial aid, grants or loans, be employed by the federal government, be admitted to public colleges or universities, or, in some states, obtain a driver's license.

Involuntary servitude: Many American libertarians oppose conscription and call for the abolition of the Selective Service System, arguing that impressment of individuals into the armed forces amounts to involuntary servitude. For example, Ron Paul, a former U.S. Libertarian Party presidential nominee,  has said that conscription "is wrongly associated with patriotism, when it really represents slavery and involuntary servitude". The philosopher Ayn Rand opposed conscription, opining that "of all the statist violations of individual rights in a mixed economy, the military draft is the worst. It is an abrogation of rights. It negates man's fundamental right—the right to life—and establishes the fundamental principle of statism: that a man's life belongs to the state, and the state may claim it by compelling him to sacrifice it in battle."
In 1917, a number of radicals and anarchists, including Emma Goldman, challenged the new draft law in federal court, arguing that it was a violation of the Thirteenth Amendment's prohibition against slavery and involuntary servitude. However, the Supreme Court unanimously upheld the constitutionality of the draft act in the case of Arver v. United States on 7 January 1918, on the ground that the Constitution gives Congress the power to declare war and to raise and support armies. The Court also relied on the principle of the reciprocal rights and duties of citizens. "It may not be doubted that the very conception of a just government in its duty to the citizen includes the reciprocal obligation of the citizen to render military service in case of need and the right to compel."

Economic: It can be argued that in a cost-to-benefit ratio, conscription during peacetime is not worthwhile. Months or years of service performed by the most fit and capable subtract from the productivity of the economy; add to this the cost of training them, and in some countries paying them. Compared to these extensive costs, some would argue there is very little benefit; if there ever was a war then conscription and basic training could be completed quickly, and in any case there is little threat of a war in most countries with conscription. In the United States, every male resident is required by law to register with the Selective Service System within 30 days following his 18th birthday and be available for a draft; this is often accomplished automatically by a motor vehicle department during licensing or by voter registration.
According to Milton Friedman the cost of conscription can be related to the parable of the broken window in anti-draft arguments. The cost of the work, military service, does not disappear even if no salary is paid. The work effort of the conscripts is effectively wasted, as an unwilling workforce is extremely inefficient. The impact is especially severe in wartime, when civilian professionals are forced to fight as amateur soldiers. Not only is the work effort of the conscripts wasted and productivity lost, but professionally skilled conscripts are also difficult to replace in the civilian workforce. Every soldier conscripted in the army is taken away from his civilian work, and away from contributing to the economy which funds the military. This may be less a problem in an agrarian or pre-industrialized state where the level of education is generally low, and where a worker is easily replaced by another. However, this is potentially more costly in a post-industrial society where educational levels are high and where the workforce is sophisticated and a replacement for a conscripted specialist is difficult to find. Even more dire economic consequences result if the professional conscripted as an amateur soldier is killed or maimed for life; his work effort and productivity are lost.