Its units (brigades and demi-brigades, divided into battalions) were subordinated to various Polish corps and armies.
Batalion ON "Lwów II") National Defense units were composed of volunteers, some reservists and unemployed.
They were equipped with second-grade weaponry, and their goal was to support defensive operations of the regular Polish Army.
National Defense was created by an order of the Polish Ministry of Military Affairs on 5 December 1936; the brigades begun to be formed in 1937.
During the German invasion of Poland in 1939, National Defense mobilized 83 battalions (approximately 1,600 officers and 50,000 soldiers).