[1][2][3] In 1922 he graduated in law at the Sapienza University of Rome, after which he practiced as a lawyer in a firm in Milan; there he met the reformist socialist leader Filippo Turati, who in turn introduced him to Giacomo Matteotti, of whom he became a friend and collaborator until his murder by Fascists in 1924.

[2][3][5] In early December 1943 he made contact with British officers, who had reached Casoli in Abruzzo, and submitted his proposal for the creation of an apolitical corps of volunteers that would fight alongside the 8th Army for the liberation of Italy.

[1][3][8] On 20 February Troilo, with a group of twenty men, managed to repel a series of German attacks on Fallascoso, a hamlet of Torricella Peligna located on the Gustav Line, and eight days later the Banda Patrioti della Maiella was officially recognized as a military unit by Marshal of Italy Giovanni Messe, chief of staff of the Italian Co-belligerent Army, and formally attached to the 209th Infantry Division.

[1][3][11] Even after the liberation of Abruzzo, where its members had been recruited, in June 1944, the Brigade continued fighting alongside the 8th Army through the Marche and Emilia Romagna, as part of the II Polish Corps, participating in the battle of Bologna in April 1945.

Its vanguards entered Asiago in Veneto on 1 May 1945, one day before the surrender of Caserta; by this point, the Brigade had grown to a strength of 1,500 men, and many more volunteers had had to be turned down do to the lack of weapons and equipment to arm them.

The news of his replacement with the prefect of Turin Vincenzo Ciotola, a career official, caused a harsh reaction from the left, which occupied the prefecture of Milan with its militants - including former armed partisans - led by Giancarlo Pajetta, while Socialist mayor Antonio Greppi (an old acquaintance of Troilo, who had attended the same Socialist circles in the early 1920s) and 156 mayors of the municipalities of the Milanese hinterland resigned en masse in protest.

[1][3] Despite the role he had played in the fight for Italy's liberation, Troilo subsequently refused any political and military honor, including a war pension, believing that he had fulfilled his duty.