During World War II, why were people of Japanese descent living in the United States forced to relocate to internment camps?

In February, 1942, two months after Japan had attacked Pearl Harbor, President Franklin D. Roosevelt signed Executive Order 9066, sending over 120,000 Japanese-American people to 10 internment camps located away from the West Coast. After Pearl Harbor, the press and politicians began to suggest that Japanese-Americans would participate in so-called "Fifth Column" activity in which they would help the Japanese government through espionage. Relying more on racist arguments than on any concrete evidence, public opinion...

In February, 1942, two months after Japan had attacked Pearl Harbor, President Franklin D. Roosevelt signed Executive Order 9066, sending over 120,000 Japanese-American people to 10 internment camps located away from the West Coast. After Pearl Harbor, the press and politicians began to suggest that Japanese-Americans would participate in so-called "Fifth Column" activity in which they would help the Japanese government through espionage. Relying more on racist arguments than on any concrete evidence, public opinion condemned Japanese-Americans as unpatriotic and more connected to their mother country than to the United States. Almost two-thirds of the people interned were Nisei, or people born in the United States. They had never seen Japan and were therefore not likely to be more loyal to Japan than to the United States. 

Another reason behind the internment was clearly racism. While about 150,000 people of Japanese descent lived in in Hawaii, only about 1,500 were interned because there was less racism against Japanese people in Hawaii. On the West Coast, however, there was a longstanding tradition of racism against Asians. For example, the Immigration Act of 1924 banned immigration from Japan and many other Asian countries. People who were as little as one-sixth Japanese were interned, supporting the idea that internment was motivated more by racism than any military necessity. German-Americans, on the other hand, were never interned, again suggesting that racism played a large role in the decision to intern Japanese-Americans. Finally, many people on the West Coast had long feared competition from Japanese-American farmers and businesspeople, and internment of the Japanese-Americans removed them as competition for the duration of the war.