"Valuable training
Some argue that peacetime conscription is an ideal tool for teaching a population basic, important skills such as first aid, swimming, wilderness survival and so on. However, it can also be argued that these skills could better be taught in the public school system than during mandatory service.<>
The draft as protection against democracy-destroying military coups
Some argue that conscription should be connected to democracy. A professional army can possibly become a dangerous state-within-a-state. Military virtues such as obedience to orders and respect for the chain of command can possibly be abused by aspiring dictators. Armed forces can attract—consciously or unconsciously—people who prefer authoritarian systems.
The army can even become the only chance for a job and decent life in times of unemployment (this was crucial in the rise of Japanese militarism), or for despised minorities. Such people may come to regard the army as their home and elevate it above the state.<>
Personnel diversity
Perhaps the kind of people who most strongly want to be in the military are not always the only kind of people who are needed in it. Conscripts come from various backgrounds and might have differing opinions and views. A diverse group is arguably more likely to succeed at any task. Still, the frequently lower morale and experience of conscripts may make them less useful in actual combat situations. This has been witnessed in the Vietnam War and Soviet-Afghan War.<>
Conscript quality
The manpower quality of a conscript force is considered poor in many countries. However, in some countries with conscription, the personnel diversity of the conscript force is considered its greatest strength. Admittedly, there are persons who would not be employed by a professional force, but these are a minority, and can be discharged for medical reasons in extreme cases.<>
Political and moral motives
Jean Jacques Rousseau argued vehemently against professional armies, feeling it was the right and privilege of every citizen to participate to the defence of the whole society and a mark of moral decline to leave this business to professionals. He based this view on the development of the Roman republic
which came to an end at the same time as the Roman army changed from a conscript to professional force....
Economics
In a very large war, (such as WW2) raising a large enough volunteer military would require dramatic increases in taxes or budget deficits. In such cases conscription can have lower negative impact than the impact of these higher taxes and be more equitable. (Higher taxes would penalise those out of service much more than those in.) Indeed research into fiscal impacts of conscription in WW2 suggest a volunteer army raised to the same size would have had worse economic impact in terms of economic growth."...
Countries with mandatory military service:
Austria
Belarus
Bermuda
Brazil
Bulgaria
Chile
China (PRC)
Croatia
Cyprus
Denmark
Egypt
Eritrea
Finland
Germany
Greece
Iran
Israel
Korea, South
Lebanon
Malaysia
Mexico
Norway
Poland
Russia
Serbia and Montenegro
Singapore
Sweden
Switzerland
Taiwan (ROC)
Turkey
Ukraine
Venezuela
http://en.wikipedia.org/wiki/Conscription