1941: The attack on Pearl Harbor interrupted Donald Keene’s Japanese studies at Columbia University. Japanese in the United States were classified as enemy aliens, and the day after the attack, New York police detained Keene’s teacher, Tsunoda Ryūsaku. Japanese residents were suspected of gathering information about American defence facilities, although the most serious evidence against Tsunoda seems to have been that “he had been observed taking long walks without a dog”.
Source: Donald Keene, The Blue-Eyed Tarōkaja: A Donald Keene Anthology, ed. J. Thomas Rimer (1996), pp. 8–9