The Department of Defense. This Department is headed by the Secretary of Defense. Examples of this from history would be when forces like the National Guard were called out to perform various tasks like guarding Little Rock High School and the Little Rock Nine, or the when they were sent to Kent State for the Vietnam protests, or the current help in enforcing and guarding the Mexican Border. Not all the occasions worked out. Their deployments are often highly contentious.
After the purchase, the United States were split into 2. The North (anti-slavery people), and the South (pro-slavery people). There was a imaginary line that was drawn (36th parallel) which states that any state north of it shall be free and any state south of it shall stay as a slave state.
