Conscription, also called draft, is when a government forces people to join the armed forces. Usually, only men are conscripted, but in Israel, women are as well. A soldier who has been forced to serve in the army is called a conscript. Conscription is a very old way to build up armies, but also usually very unpopular, since very few men enjoy fighting and killing other people. Historically conscription was called levy, but it was so unpopular that it was used only when the country was in really dire danger.
18th century Prussia had a conscript army but the first large, modern conscript army was the French Grand Army in the French Revolution. The leaders drafted all French men into the army. The result was that the French army was five times larger than that of neighbour countries, and the sheer numbers often won battles. While the French soldiers were less well trained and equipped than the soldiers of the neighbour armies, they were so many that they could win. Conscription became the universal way of making up the armies after the French Revolution. Almost all the powerful armies in the world except United Kingdom were conscripted armies. Without conscription, the large armies of World War One and World War Two would have been impossible to form.
Conscription armies are large, but they are often poorly equipped and trained and have poor morale. In combat they usually suffer many casualties. Usually conscripts serve with little pay and many are treated little better than slaves. Conscription can be considered as a form of forced labour. In many countries, young men who refuse to join the army are sentenced to prison. Many people "dodged" or illegally avoided conscription during the Vietnam War in the United States.
There are arguments for conscription. Some see it as fair, since everyone shares the burden of service. A small country with few people can make up a large enough army by conscription. If a country is in the midst of hostile neighbours and war can break up at any time, or if the country is a buffer state (= is located between two military blocks), training all available young people as soldiers can be a good idea.
The alternatives for conscription are militia system, as in Switzerland, or professional army made up from volunteers. The United States gave up conscription during the Cold War. The Vietnam War proved so unpopular that the Army no longer wanted conscripts, but volunteers, which have better motivation to serve. Most other Western World countries followed the American example and gave up conscription. Some American countries now have all-volunteer army and in Europe universal conscription remains only in some countries like Finland, Russia and Turkey.
People who oppose conscription because of pacifism idea are called conscientious objectors. Some countries still draft conscientious objectors, but give them jobs where they will not have to fight in combat.