American Buddhism during World War II imprisonment refers to the Japanese American Buddhist experience between 1942 and 1945 when persons of Japanese ancestry, commonly known as Nikkei Amerikajin, were imprisoned. A discussion of the Nikkei Buddhist experience includes the experiences of Euro-American convert Buddhists who supported them during the imprisonment period. Immediately after the Imperial Japanese Navy attacked Pearl Harbor on December 7, 1941, the Federal Bureau of Investigation (FBI) arrested and interned Japanese Buddhist priests and other leaders of Japanese communities in the United States. In March 1942, the Western Defense Command designated the three West Coast states (Washington, Oregon, and California) and Arizona as Military Area No. 1, from which all persons of Japanese descent, and alien Germans and Italians, were forcefully removed. Following Executive Order 9066 signed by President Franklin D. Roosevelt, the US government removed approximately 120,000 Japanese Americans from the aforementioned military zone and incarcerated them in relocation centers built throughout the continental United States. During that time, the Nikkei community consisted primarily of the Issei, the first generation of Japanese immigrants, and the Nisei, their American-born children. As Tetsuden Kashima defines, the word “internment” refers to the imprisonment of enemy aliens, such as the Issei Japanese nationals, by the Department of Justice and the US Army, while the term “incarceration” refers to the confinement of the Nikkei, including a great number of the Nisei American citizens, by the War Relocation Authority. The word “imprisonment” designates the entire process consisting of internment and incarceration. The study of American Buddhism during World War II is still in its early stages. Finding records and documents related to this subject from the large collections on Japanese American imprisonment is not an easy task. While the National Archives in Washington, DC, maintains the majority of primary sources dealing with Japanese American relocation and incarceration, other institutions, such as the Japanese American National Museum, the University of California-Los Angeles, and museums built around the sites of internment camps, also preserve records. Some of the primary sources are written in Japanese and are located in Japan, which is another stumbling block for researchers who do not read Japanese. Duncan R. Williams’s forthcoming book, American Sutra: Buddhism and the World War II Japanese American Experience, however, will change the current state of scholarship on Japanese American Buddhism during World War II. The forceful relocation of Japanese American Buddhists served to weaken their long-standing efforts to make their ethno-religious practices accepted by America’s general public. Mass incarceration, however, forced the Japanese American Buddhists to further Americanize their religion, generated a set of new Buddhist practices, and gave them opportunities to reflect on their national identities. Buddhist faith and cultural practices associated with Japanese Buddhism contributed to ethnic solidarity, even though the Japanese American community was divided over the issue of US patriotism. During the postwar period, Japanese American Buddhists initiated a campaign to improve their image in the United States and to honor the Nisei Buddhist soldiers who fought during World War II. The formation of American Buddhism was closely connected to the development of US political ideology.