A conscientious objector (CO) is an "individual who has claimed the right to refuse to perform military service" on the grounds of freedom of thought, conscience, and/or religion. In general, conscientious objector status is only considered in the context of military conscription and is not applicable to volunteer military forces.
In some countries, conscientious objectors are assigned to an alternative civilian service as a substitute for conscription or military service. Some conscientious objectors consider themselves pacifist, non-interventionist, non-resistant, or antimilitarist.
The international definition of conscientious objection officially broadened on March 8, 1995 when the United Nations Commission on Human Rights resolution 1995/83 stated that "persons performing military service should not be excluded from the right to have conscientious objections to military service." That definition was re-affirmed in 1998, when the United Nations Office of the High Commissioner for Human Rights document called "Conscientious objection to military service, United Nations Commission on Human Rights resolution 1998/77" officially recognized that "persons performing military service may develop conscientious objections."
Read more about Conscientious Objector: Introduction, Religious Motives, Selective Conscientious Objection, Alternatives For Objectors, Conscientious Objection in Professional Forces