Corporal is a military rank in use in some form by most militaries and by some police forces or other uniformed organizations. Within NATO, each member nation's corresponding military rank of corporal is combined under the NATO-standard rank scale code OR-4.orporal is the second lowest of the non-commissioned officer ranks in the Australian Army, falling between lance-corporal and sergeant. A corporal is usually a section commander, and is in charge of 7-14 soldiers of private rank.