[3] According to his obituary in The Guardian, Guerra first started writing poetry when interned in a prison camp in Germany, after being rounded up at the age of 22 with other antifascists from Santarcangelo.

[3] During this time he met Elio Petri, the future director of Investigation of a Citizen Above Suspicion (1970), who worked as assistant to Giuseppe De Santis.

Guerra was able to get his first screenwriting credit after he and Petri went to the Abruzzi mountains to find out about wolf-hunting; "Though they discovered that wolf hunters no longer existed, De Santis went ahead anyway with the film, Uomini e Lupi (Men and Wolves, 1957)".

[citation needed] He worked with such filmmakers as Michelangelo Antonioni, in L'Avventura, La Notte, L'Eclisse, Red Desert, Blowup, Zabriskie Point and Identification of a Woman; Federico Fellini, in Amarcord; Theo Angelopoulos, in Landscape in the Mist, Eternity and a Day and Trilogy: The Weeping Meadow; Andrei Tarkovsky, in Nostalghia and Voyage in Time; and Francesco Rosi, in The Mattei Affair, Lucky Luciano, Illustrious Corpses and Christ Stopped at Eboli.

In 1990, Guerra in collaboration with Giovanni Urbinati to create the exhibition “La Cattedrale dove va a dormire il mare/The Cathedral where the sea goes to sleep” [5] at the deconsecrated church in Budrio near Bologna.