“Assembly center” was the official government name for the temporary detention facilities—often converted fairgrounds or race tracks—to which Japanese American evacuees were sent on the way to being sent to relocation centers.

An “enemy alien” refers to a foreign-born resident in a country that is at war with the resident’s native or ancestral country. After the US declared war against Japan in December 1941, people born in the Axis countries (Japan, Germany, and Italy) who were resident in the US became defined as enemy aliens and were thus subject to being searched, questioned, arrested, or removed.

One of three types of official presidential documents, an “executive order” is a “signed, written, and published directive from the President of the United States that manages operations of the federal government” (“What Is an Executive Order?” American Bar Association, 2021). Executive orders are numbered consecutively, e.g., Order 9066. They are not legislation, do not require approval by Congress, and can only be overturned or formally terminated by another executive order by a sitting president.