A Jew of Hungarian origin, Mandel-Mantello was known to support Carl Lutz's efforts to protect the persecuted of Budapest. To conceal the transfer of the document - an illegal act for a Swiss official - Lutz had it forwarded to Switzerland with a letter from the Jewish Agency in Budapest, whose office was housed in the Swiss premises.
In mid-June 1944, Romanian diplomat Florian Manoliu smuggled the Auschwitz protocols out of Hungary back to Switzerland and handed them over to the Consulate General of Salvador. Deeply troubled by the content, Mandel-Mantello wrote a summary of the Protocols and made 1'000 copies to be sent to Jewish communities, members of Parliament and influencers. The well known Swiss theologian Karl Barth, in Basel, and the Secretary General of the World Council of Churches W.A. Visser’s Hooft, in Geneva, signed an open letter calling upon Hungary to stop deportations. The topic was raised in sermons across churches in Switzerland and made headlines in the Swiss media, despite the strict censorship imposed by the Swiss Government. A public demonstration took place in Basel.
A copy was also sent by Mandel-Mantello to foreign news agencies in Zurich. The international outcry was considerable – a public demonstration was held at Madison Square Garden in New York - and forced the Allies and neutral States to take a stand, reluctantly. The King of Sweden sent a letter to the Hungarian authorities.
The American air force bombed Budapest. On June 26, President Roosevelt, campaigning for reelection at the time, sent a stern letter to the Hungarian leader, Regent Horthy, urging him to stop deportations. Ironically, this letter was given to the Hungarian authorities by Carl Lutz himself, the actual whistleblower. The Vice-Consul was in charge of protecting American interests in Hungary.