In exchange for its participation with the Triple Entente and in the event of victory, Italy was to obtain Austro-Hungarian territory in northern Dalmatia, including Zara, Sebenico and most of the Dalmatian islands.

With the arrival of the Royal Italian Army in the city within the framework of the occupation of the eastern Adriatic on 4 November 1918, the Italian faction (that was the huge majority in the city) gradually assumed control, a process which was completed on 5 December when it took over the governorship.

Within a few weeks, Benito Mussolini required the newly formed puppet-state, the so-called Independent State of Croatia (NDH) to hand over almost all of Dalmatia (including Spalato/Split) to fascist Italy under the Rome Treaties.

However, just four days later on 12 September 1943, "Il Duce", was rescued by a German military raid from his secret prison on the Gran Sasso mountain, and formed the Nazi-puppet Italian Social Republic in the north of the country.

The city was prevented from joining the NDH on the grounds that Zara itself was not subject to the conditions of the Rome Treaties.

[4] On October 31, 1944, the Partisans seized the city, until then an official part of Mussolini's Italian Social Republic.

At the start of World War II, Zadar had a population of 24,000 (nearly all Dalmatian Italians) but, by the end of 1944, this had decreased to 6,000.

But with the enlargement in 1941 the number grew to 20 (first in Italian the official name and then in Croatian the actual):[7] The municipality-island of Lagosta/Lastovo was transferred to the Province of Spalato.