Like many futurists, he took an irredentist position during World War I. Ungaretti debuted as a poet while fighting in the trenches, publishing one of his best-known pieces, L'allegria ("The Joy").

After spending several years in Brazil, he returned home during World War II, and was assigned a teaching post at the University of Rome, where he spent the final decades of his life and career.

[2] This period marked his debut as a journalist and literary critic, with pieces published Risorgete, a journal edited by anarchist writer Enrico Pea.

[2] He was also in contact with the Italian expatriates, including leading representatives of Futurism such as Carlo Carrà, Umberto Boccioni, Aldo Palazzeschi, Giovanni Papini and Ardengo Soffici,[6] as well as with the independent visual artist Amedeo Modigliani.

[7] Upon the outbreak of World War I in 1914, Ungaretti, like his Futurist friends, supported an irredentist position, and called for his country's intervention on the side of the Entente Powers.

[8] The conflict also made Ungaretti discover his talent as a poet, and, in 1917, he published the volume of free verse Il porto sepolto ("The Buried Port"), largely written on the Kras front.

[10] Although depicting the hardships of war life, his celebrated L'Allegria was not unenthusiastic about its purpose (even if in the poem "Fratelli", and in others, he describes the absurdity of the war and the brotherhood between all the men); this made Ungaretti's stance contrast with that of Lost Generation writers, who questioned their countries' intents, and similar to that of Italian intellectuals such as Soffici, Filippo Tommaso Marinetti, Piero Jahier and Curzio Malaparte.

He was present in the Paris-based Dadaist circle led by Romanian poet Tristan Tzara, being, alongside Alberto Savinio, Julius Evola, Gino Cantarelli, Aldo Fiozzi and Enrico Prampolini, one of the figures who established a transition from Italian Futurism to Dada.

In his essays of 1926–1929, republished in 1996, he repeatedly called on the Duce to direct cultural development in Italy and reorganize the Italian Academy on fascist lines.

[8] Meanwhile, he contributed to a number of journals and published a series of poetry volumes, before becoming a foreign correspondent for Gazzetta del Popolo in 1931, and traveling not only to Egypt, Corsica and the Netherlands, but also to various regions of Italy.

[18] The new trend, inspired by both Symbolism and Futurism, had its origins in both Il porto sepolto, where Ungaretti had eliminated structure, syntax and punctuation, and the earlier contributions of Arturo Onofri.

[19] At the close of the war, following Mussolini's downfall, Ungaretti was expelled from the faculty owing to his fascist connections, but reinstated when his colleagues voted in favor of his return.

[8] L'Allegria, previously called L'Allegria di Naufragi, is a decisive moment of the recent history of Italian literature: Ungaretti revises with novel ideas the poetic style of the poètes maudits (especially the broken verses without punctation marks of Guillaume Apollinaire's Calligrammes and the equality between verse and a single word),[20] connecting it with his experience of death and pain as a soldier at war.

M’illumino d’immenso I illuminate (myself) with immensity A famous poem regarding the First World War is Soldati (soldiers), which emblematically and emotionally describes their feelings of uncertainty and fear:

Si sta come d'autunno sugli alberi le foglie It's like being in the autumn on the trees the leaves In the successive works he studied the importance of the poetic word (marked by Hermeticism and symbolism), as the only way to save the humanity from the universal horror, and was searching for a new way to recuperate the roots of the Italian classical poetry.

[23] His last verses are on the poem l'Impietrito e il Velluto, about the memory of the bright universe eyed Dunja, an old woman that was house guest of his mother in the time of his childhood.