Born in a small town of Piemonte, of waldensian religion, he enrolled in the Italian Army when young and fought in the conquest of Libya in 1911. In 1935 went to the conquest of Ethiopia and in 1939 of Albania, where he distinguished himself; from 1937 to 1941 he was chief of staff of the 3rd Alpine Division Julia.
In 1939 he published a book titled "Il grande capo d'una grande impresa", edited by "Societa Studi Valdesi", about the qualities of the military leader Duca d'Aosta in 1690 against the French. In 1942 as a Brigadier general he went to the Soviet Union in the ranks of the Corpo d'Armata Alpino, as part of the Armata Italiana in Russia.
In January 1943 Giulio Martinat was leading the Italian forces during the Battle of Nikolayevka, trying to open a retreat route for the surviving Italian soldiers trying to reach safety, when he was killed in combat; for this he received the Italian Gold Medal of Military Valor. Upon seeing the Alpini of the Edolo battalion, Martinat reportedly said "with the Edolo [Battalion] I started, with the Edolo [Battalion] I want to end" (the Edolo battalion had been the first unit where he had served); he took up a rifle, led his men in battle, and was killed. His sacrifice opened the road for the Italian withdrawal at the Battle of Nikolayevka.
- Bedeschi, Giulio. Centomila gavette di ghiaccio. Mursia editore. Milano, 1994 ISBN 88-425-1746-1
- Fellgiebel, Walther-Peer (2000) . Die Träger des Ritterkreuzes des Eisernen Kreuzes 1939–1945 — Die Inhaber der höchsten Auszeichnung des Zweiten Weltkrieges aller Wehrmachtteile [The Bearers of the Knight's Cross of the Iron Cross 1939–1945 — The Owners of the Highest Award of the Second World War of all Wehrmacht Branches] (in German). Friedberg, Germany: Podzun-Pallas. ISBN 978-3-7909-0284-6.