The number and grades of officers and enlisted persons in the state staff and detachment shall be as prescribed by federal law, but in case of war, invasion, insurrection, civil disturbance or imminent danger of any of the foregoing, the governor may temporarily increase the force to meet the emergency, and retired officers who are physically qualified may be assigned to emergency duty. All officers appointed to the state staff and detachment shall have had previous military service and shall be selected and appointed by the adjutant general and commissioned by the governor. The enlisted persons shall be recruited and administered by the detachment commander.