Query: Who were the majority of names on the custodial detention list?
Context: In 1939, the Bureau began compiling a custodial detention list with the names of those who would be taken into custody in the event of war with Axis nations. The majority of the names on the list belonged to Issei community leaders, as the FBI investigation built on an existing Naval Intelligence index that had focused on Japanese Americans in Hawaii and the West Coast, but many German and Italian nationals also found their way onto the secret list. Robert Shivers, head of the Honolulu office, obtained permission from Hoover to start detaining those on the list on December 7, 1941, while bombs were still falling over Pearl Harbor.