Issues of war and peace are the most momentous any nation can face, and at times of crisis, many nations turn to their military for leadership.
Not in democracies.
In democracies, questions of peace and war or other threats to national security are the most important issues a society faces, and thus must be decided by the people, acting through their elected representatives. A democratic military serves its nation rather than leads it. Military leaders advise the elected leaders and carry out their decisions. Only those who are elected by the people have the authority and the responsibility to decide the fate of a nation.
This idea of civilian control and authority over the military is thus, fundamental to democracy.
Civilians need to direct their nation's military and decide issues of national defense not because they are necessarily wiser than military professionals, but precisely because they are the people's representatives and as such are charged with the responsibility for making these decisions and remaining accountable for them.
The military in a democracy exists to protect the nation and the freedoms of its people. It does not represent or support any political viewpoint or ethnic and social group. Its loyalty is to the larger ideals of the nation, to the rule of law, and to the principle of democracy itself.
Civilian control assures that a country's values, institutions, and policies are the free choices of the people rather than the military. The purpose of a military is to defend society, not define it.
Any democratic government values the expertise and advice of military professionals in reaching policy decisions about defense and national security. Civilian officials rely upon the military for expert advice on these matters and to carry out the decisions of the government. But only the elected civilian leadership should make ultimate policy decisions -- which the military then implements in its sphere.
Military figures may, of course, participate fully and equally in the political life of their country just like any other citizens - but only as individual voters. Military people must first retire from military service before becoming involved in politics; armed services must remain separate from politics. The military are the neutral servants of the state, and the guardians of society.
Ultimately, civilian control of the military ensures that defense and national security issues do not compromise the basic democratic values of majority rule, minority rights, and freedom of speech, religion, and due process. It is the responsibility of all political leaders to enforce civilian control and the responsibility of the military to obey the lawful orders of civilian authorities.