American soldiers in the Pacific often deliberately killed Japanese soldiers who had surrendered. According to Richard Aldrich, a professor of history at the University of Nottingham. who has published a study of the diaries kept by United States and Australian soldiers, they sometimes massacred prisoners of war. Dower states that in "many instances ... Japanese who did become prisoners were killed on the spot or en route to prison compounds". According to Aldrich it was common practice for U.S. troops not to take prisoners. This analysis is supported by British historian Niall Ferguson, who also says that, in 1943, "a secret [U.S.] intelligence report noted that only the promise of ice cream and three days leave would ... induce American troops not to kill surrendering Japanese".