1. The Holy See was well informed about nearly all aspects of European and North American diplomacy. Reports from the major European capitals were mostly accurate and nuanced. Vatican diplomats were skilled practitioners of their craft and nearly all had regular access to the corridors of power, as well as often being sought after as "men of influence". In the months leading to the war, the Vatican was informed as to the developments of most diplomatic proposals, counter-proposals, propaganda, overtures made to the Soviet Union by the British and French as well as the Germans, and of the growing unease that war was inevitable. Of all the "players" in the field at this time I believe the Holy See was arguably the best informed. This did not change after September 1939.
2. From many quarters in Europe, including Germany, as well as the USA, Pope Pius XII was seen as someone of great moral influence whose voice and opinion was sought after. This is not to be confused with heeding the voice of the Pope - he was just as readily ignored - but Pius' views were asked. There is a near consensus that the Pope was the most significant person to speak on peace in Europe, a voice of moderation and, most significantly, a voice above politics and power systems.
3. Pius XII's attempts at brokering peace in the months before the outbreak of the war were regarded positively by the European powers, including Germany. However, the limits of papal power were obvious when papal proposals ran up against national interests. Already there was criticism that Pius' silence in the face of the Italian invasion of Albania and the ever-increasing anti-Catholic actions of the Nazis, his enthusiastic message to Franco at the end of the Spanish Civil War and seeming lack of interest in an ecumenical prayer crusade for peace. The Vatican argued that the pope must remain above all political matters; and Catholic teaching in 1939 was not in favour of joint prayer with the "separated brethren".
4. Within the first months of Pius' pontificate there are the beginnings of a relationship with President Roosevelt that would endure until FDR's death in 1945.
5. Of all the Vatican diplomats, Cesare Orsenigo in Germany appears to have been the weakest. Orsenigo's reports convey much information that suggests a sympathy for the German government outside of matters of particular relevance to the Church. The nuncio also appears to have shown willingness to accept German news reports as reliable even to the point of advising Rome that there was no likelihood of war despite Polish "provocations" on the border. In Italy the Pope's personal contact with Il Duce, Fr Tacchi Venturi reported the opposite and quoted directly from Mussolini. Nuncio Borgongini Duca reported the opposite from Mussolini's son-in-law and Foreign Minister, Galeazzo Ciano.
6. As hopes for a peace conference faded, the attention of the diplomats turned to the increasing tension between Poland and Germany. Cardinal Maglione advised the nuncios in France and Germany that he had sent instructions to Nuncio Cortesi in Warsaw asking the Poles to be prudent in their relations with Germany.
7. As summer progressed the Vatican grew more and more concerned at the likelihood of war. Pleas were made to Poland to be "reasonable" and "moderate" and the Vatican listened closely to all proposals to resolve the question of Danzig and The Corridor.
8. There are occasional quirky moments. Nuncio Valerio Valeri was convinced that anti-Catholic and anti-papal feeling in France came from Freemasonry.