From Longman Dictionary of Contemporary Englishactive serviceˌactive ˈservice (also active duty) noun [uncountable] the work that soldiers do in a war Powell was declared unfit for active service.on active service/duty More than 20,000 women are on active duty.
Examples from the Corpus
active service• Three times during that year, Cottle was called before medical boards to assess his fitness for active service.• In 1914 Powell was declared unfit for active service, but joined the Admiralty in 1916.• It was rather like being in the army on active service.• They had two sons, one of whom died on active service in 1944, and one daughter.• In his early years John the younger saw active service abroad.• How often, when and where women-only units would see active service is anybody's guess.on active service/duty• It was rather like being in the army on active service.• We accepted this as just one of the hazards of being on active service.• They had two sons, one of whom died on active service in 1944, and one daughter. 