[1][2] After the end of the war he returned to Trieste, now part of Italy, where he taught at the "Petrarca" high school until 1925; in the same years he joined the anti-Bolshevik committees and participated in D’Annunzio's occupation of Fiume.

He aligned himself with the moderate faction, linked to economic groups and the liberal-national party, and in 1926 he became secretary of the Fascist Industrial Union of Venezia Giulia, becoming the point of reference between the industrialists of the region and the PNF.

[1][2][3] Between 1924 and 1927 he did not carry out significant political activity, dedicating himself to teaching literature at the Francesco Petrarca Lyceum of Trieste and becoming dean of the local folk high school.

In 1931 he also founded the magazine La Porta Orientale, aligned with irredentist and anti-slavic positions; after the promulgation of the Italian racial laws in 1938 it also hosted anti-Jewish articles.

After the fall of Fascism on 25 July 1943, he occasionally continued to go to his office of the Industrial Union, while undergoing the blocking of current accounts and a house search ordered by the new authorities who had settled in Trieste on behalf of the Badoglio government.

Throughout the region the Germans exploited the contrasts between Slavs and Italians according to a divide and rule policy; in the villages around Trieste, with a Slavic majority, some Slovenian and Croatian schools were reopened, and the free circulation of newspapers from Ljubljana was allowed.

Coceani, as the leader of the local Italian nationalists, repeatedly protested with the German authorities, and especially with SS General Odilo Globocnik, whom he considered to be the real originator of these policies, effectively ruling over Rainer.

Coceani favored Italian magazines, especially those that referred to the anti-Austrian irredentist tradition, while rejecting requests to authorize similar publications by the Slovene minority; only some radio programs in Slovenian language were allowed.

The task of this Civic Guard was initially the recovery of the weapons abandoned by the Royal Italian Army after the armistice, but Coceani and Pagnini planned to use it for the protection of the city from the Yugoslav partisans, even in collaboration, if possible, with the local Committee of National Liberation.