"The documents ... constitute an extensive selection from the large body of correspondence of Robert Lansing, former secretary of state, which was secured for the files of the Department of State following Mr. Lansing's death ... A certain number of closely related documents from other official sources ... have been included. The papers here published represent, therefore, an additional selection of documents from the period 1914 through 1920 bearing on subjects which have already been presented in the volumes of Foreign relations hitherto published dealing with that period." - Pref.