In 1906 De Martino created the Istituto coloniale italiano, in order to promote the development of the Italian colonies and their management.

[2] Appointed senator (March 4, 1905), De Martino made long journeys to the Indies and to eastern and northern Africa and continued his propaganda with speeches and publications including the book Cyrene and Carthage (Bologna 1908).

Appointed governor of Somalia (January 11, 1910), he began a policy of economic strengthening of that colony and of affirmation and expansion of Italian dominion, starting studies for the construction of a port, a road network and a railway towards the interior, making the first attempts at white colonization, establishing the regime of agricultural concessions on the Giuba and initiating the first contacts with the populations of the Oltre-Giuba.

The dams of the Scebeli, the Genale dam and the relative state experimental company, and the purchase of Mahaddei-Uen on the Scebeli, Bur Acaba and Baidoa date back to him.

As governor of the Colony of Eritrea (1916-1919), De Martino gave great impetus to public works, such as the construction of the customs sheds of Massawa, the building development of Asmara, the extension of the railway line in Cheren and beyond, towards the Gasc , the plants of the first mountain hydroelectric basin with the Belesa dam, and the industrial agricultural setting of Tessenei.