What use was made of this order, which set up military areas where the Secretary of War controlled who would enter the place, who would leave or stay, and who was excluded?
It sounds like you are referring to Executive Order 9066, which was issued by President Franklin D. Roosevelt during World War II. This order authorized the forced relocation and internment of Japanese Americans living on the West Coast of the United States.
The military areas referred to in the order were established to exclude Japanese Americans from certain areas deemed critical to national defense. The Secretary of War was given the authority to determine who would be excluded from these areas and who would be allowed to remain.
As a result of the order, over 120,000 Japanese Americans, two-thirds of whom were American citizens, were forcibly removed from their homes and placed in internment camps for the duration of the war. The order was later recognized as a grave violation of civil liberties and constitutional rights, and reparations were provided to surviving Japanese American internees in the 1980s.