NSD meaning in Military and Defence ?

National security directives are presidential directives issued for the National Security Council (NSC). Starting with Harry Truman, every president since the founding of the National Security Council in 1947 has issued national security directives in one form or another, which have involved foreign, military and domestic policies. National security directives are generally highly classified and are available to the public only after "a great many years" have elapsed. Unlike executive orders, national security directives are usually directed only to the National Security Council and the most senior executive branch officials, and embody foreign and military policy-making guidance rather than specific instructions.