[from his confession to having been a Soviet spy, January 27, 1950] At first I thought that all I would do would be to inform the Russian authorities that work upon the atomic bomb was going on. They wished to have more details and I agreed to supply them. I concentrated at first mainly on the product of my own work, but in particular at Los Alamos I did what I consider to be the worst I have done, namely to give information about the principle of the design of the plutonium bomb...The last time when I handed over information was in February or March 1949.
