Upon outbreak of World War I, authorities in Austria-Hungary interned Grisogono together with his brother Ivo, and writers Ante Tresić Pavičić and Niko Bartulović in Maribor and then in Zadar until his release in 1917.
[1] The National Council appointed Grisogono a deputy member of the three-member provincial government of the former Austro-Hungarian crown land of Dalmatia.
The government consisted of Ivo Krstelj, Josip Smodlaka, and Vjekoslav Škarica, while Grisogono, Uroš Desnica, and Jerko Machiedo were appointed their deputies.
[1] In 1919, Grisogono took part in founding of the Democratic Party of the newly-established union-state of the South Slavs, the Kingdom of Serbs, Croats and Slovenes (later renamed Yugoslavia).
The purported purpose of the meeting was to ensure that Maček does what he can to prevent atrocities against Serbs in exchange for Mihailović's assurance of no reprisals against Croats.
The letter was written in early 1942 amid numerous rumours (some factual, others fabricated) of atrocities committed in the context of genocide of Serbs in the NDH.
The purpose of the letter and its attribution to Grisogono was to make the rumours more credible since they were alleged to have come from a reputable public figure of Croat descent.
While condemning Ustaše crimes and passivity of individuals within the Catholic Church, Grisogono was outraged that his reputation was used to assign collective responsibility and spread hatred between Croats and Serbs.
[3] Grisogono denied his authorship of the letter in an article published by Time and Tide in 1953 once again, but the forgery was touted as authentic in Yugoslavia regardless.