When Japan attacked Pearl Harbor on Dec. 7, 1941, government officials immediately placed Hawaii under martial law and became concerned about the Japanese-Americans who lived on the West Coast of the United States. Intelligence gathered before the attack indicated that Japan was recruiting spies and had already secured a spy network there [source: Kops]. However, whether certain officials knew about this -- and whether it motivated their support for the relocation efforts -- is a matter of debate.
Immediately after the attack on Pearl Harbor, government officials rounded up who they considered potentially dangerous aliens for review. This included more than 1,500 aliens from Japan, but also some from Germany and Italy. After review, some aliens were released, and others were sent to detention camps. Soon, the government imposed curfews and travel restrictions on Japanese-Americans living on the West Coast. Meanwhile, Canada also enforced a relocation policy, which required more than 20,000 Japanese-Canadians to move from the West Coast to other regions or camps.
On Feb. 19, 1942, two months after the attack on Pearl Harbor, Roosevelt issued Executive Order 9066, which gave the military the power to designate zones in which "any or all persons may be excluded" for national defense purposes [source: FDR Library]. As a result, about 112,000 people, both first-generation (issei) and second-generation (nisei) Japanese-Americans living on the West Coast were forced to go to temporary assembly centers and then to relocation camps, regardless of citizenship. Although the executive order primarily affected Japanese living on the West Coast, it also resulted in hundreds of Italian-Americans and German-Americans being banned from zones on both coasts [source: Malkin].
With about two weeks notice at most, Japanese on the West Coast had to leave their homes behind and bring with them only what they could carry. They lived in the assembly centers (such as military barracks or repurposed fairgrounds under military control) for months until the late summer of 1942, when they were finally sent to one of 10 internment camps.