A military reserve refers to a force composed of trained individuals who are not in active military service but can be called up for duty when necessary. These individuals typically have prior military training and experience, and they remain part of a nation's defence structure, ready to reinforce active duty forces in times of crisis, such as wars, natural disasters, or other emergencies.
Military reserves provide strategic flexibility and help ensure that a country can rapidly scale up its military strength without maintaining a large active-duty force, which is often more costly. Members of the reserve often undergo periodic training to keep their skills sharp and may have civilian careers while staying prepared to be mobilized when needed.