 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.At 30 he moved to Rome and worked as a schoolteacher.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.