[Tsuneishi Keiichi of Kanagawa University had already been unearthing secrets about Japan's biological warfare (BW) program for a quarter century when he made a vital discovery about Unit 731 in summer 2005. The two memoranda he discovered from July 1947 were written by Brig. Gen. Charles Willoughby, head of GHQ's intelligence unit during the American Occupation, and found in the U.S. National Archives. The documents shed new light on GHQ's carrot-and-stick method of obtaining BW data at the outset of the Cold War as the arms race against the Soviet Union heated up. The Americans offered the Japanese scientists far more carrots—in the form of cash payments and other rewards as well as immunity from prosecution—than was previously understood.