From To The Bitter End, Hans Bernd Gisevius, 1947

Prevention! As a result of the Nuremberg Trials the skill with which Canaris prevented the murders of Generals Giraud and Weygand has become public knowledge. when Hitler censured him for letting these men escape, Canaris cleverly made use of the assassination of Heydrich to shift all the blame to the Black hangman. In the spring of 1943, when Oster head of the scheme for kidnaping both the King of Italy and the Pope, in order to prevent the fall of Mussolini, he made a brief telephone call to Canaris and hinted at what he had learned. The admiral at once emplaned from the Crimea to Berlin, and from there flew on to Venice to warn his Italian colleagues.

Boston : Houghton Mifflin, 1947, page 444.