The pigeons are registered and taken care of by a pigeon breeder (a subofficer) assisted by a soldier.
early 14c., "one who holds an office" (originally a high office), from Old French oficier "officer, official" (early 14c.), from Medieval Latin officarius "an officer," from Latin officium "a service, a duty" (see office). The military sense is first recorded 1560s. Applied to petty officials of justice from 16c.; U.S. use in reference to policemen is from 1880s.