Between the last years of the pontificate of Pius XI and the early pontificate of Pius XII, the cross-relations between the Holy See, China and Japan reached the most critical moment in the history of the 20th century. Caught between the desire to maintain an independent diplomacy from fascist Italy, which together with Japan was pressing for an official recognition of Manchukuò, and the need to have a representation for the over 150,000 Catholics, 0.5% of the population, in the occupied territory, the Holy See wavered between a persistent silence in answer to the official communication of the filo-japanese puppet state, and the final appointment of an ad tempore delegate to Manchukuò, Auguste Gaspais, in 1934. The aim of this work is to reconstruct the history of relations between the Holy See and Manchukuò, and their role in the aftermath of the war. This work will start from the reconstruction of the Holy See-Manchukuò relations as recorded in Celso Costantini's memorandum to Msr. Montini, dated 30 November 1944 (Propaganda Fide, rubr. 2411, Manchuria), and then turn the article published on the Holy See Journals and Periodical, with a particular attention ot the Osservatore Romano.