On 12 May 1912, during the Italian-Turkish War, a landing contingent ship "St. Mark" Leros raised in Leros the Italian flag. Commander of the island at that time became Lieutenant Gramatika.
From 1916 to 1918, the British used Leros as a naval base. By pact between Venizelos-Tittoni the island would return to Greece. The agreement was never ratified by the Italian parliament and languished after the Minor Asia catastrophe. The Treaty of Lausanne confirmed the Dodecanese as Italian property.
After 28 October 1922, the Italian Fascist regime actively attempted to “italianate” the Dodecanese.
At the end of 1936, these efforts were intensified by the Italian occupiers with a series of decrees regarding education (abolition of Greek schools and placing them under the control and administration of the Italian authorities), the compulsory learning of Italian language, prohibiting the exercise of professions such as doctor's, lawyer who hadn’t studied at Italian universities. De Vecchi was the military and political commander of Dodecanese during that period.
Mussolini highlighted the island as a base of utmost importance for the Italian dominance in the area, because of its strategic geographical position, combined with Lakki being the largest natural harbor in the Eastern side of the Mediterranean Sea. The Italian intervention in the island is catalytic. The mountains, military installations and a large part of Leros are announced military zone.
In this period, the main road axis with side tree planting of eucalyptus trees is constructed. In Lakki a new city with impressive buildings and infrastructure is created, its name is ‘Porto Lagos’. Today it is one of the most representative examples of Italian rationalism.
During the 31 years that the Italians remained in Leros, the fortification of Leros, as well as the construction of a major naval base at Lakki, ensured the Italian control of a region (the Aegean, the Dardanelles and the Middle East), that was vital to the Allies .
The legacy of this period remained on the island in the form of the modern town of Lakki, with its city plan and the important public and private buildings. Today, despite the decay of time, visitors can walk around the spacious streets and admire the constructions of a particular era and architectural style. Such buildings are the cyclical market with the clock, the complex of cinema theater-hotel Roma, the City Hall complex and private houses etc.