Other important , low-level and high-level ideological agents were the diplomats Laurence Duggan and Michael Whitney Straight in the State Department , the statistician Harry Dexter White in the Treasury Department , the economist Lauchlin Currie ( an FDR advisor ) , and the " Silvermaster Group " , headed by statistician Greg Silvermaster , in the Farm Security Administration and the Board of Economic Warfare . Moreover , when Whittaker Chambers , formerly Alger Hiss 's courier , approached the Roosevelt Government — to identify the Soviet spies Duggan , White , and others — he was ignored . Hence , during the Second World War ( 1939 – 45 ) — at the Tehran ( 1943 ) , Yalta ( 1945 ) , and Potsdam ( 1945 ) conferences — Big Three Ally Joseph Stalin of the USSR , was better informed about the war affairs of his US and UK allies than they were about his
Yalta
Yalta Conference
KGB