An imperfect for one-off events
The imperfetto usually describes background, states and habits. The imperfetto narrativo instead tells a single, completed event, exactly what the passato remoto or passato prossimo would normally do. It is not a mistake but a stylistic device.
The same event, two views
Passato remoto: report
Nel 1946 l'Italia divenne una repubblica.
In 1946 Italy became a republic.
The event is stated.
Imperfetto narrativo: scene
Nel 1946 l'Italia diventava una repubblica.
In 1946 Italy became a republic.
The event is shown like a freeze-frame.
The effect: the narrator briefly stops the clock and lets the reader witness the moment rather than just hear about it. English has no dedicated form for this. You translate with the simple past or, for more immediacy, with the historic present.
Without a time anchor, the reading flips
For the imperfetto to read as a one-off event, it needs a precise point in time: a date, a clock time, poco dopo, il giorno seguente. Without one, it is understood as a habit or an action in progress.
With and without an anchor
Marco lasciava la città.
Marco was leaving the city. / Marco used to leave the city.
No anchor: in progress or habitual
Il giorno dopo, Marco lasciava la città.
The next day, Marco left the city.
With an anchor: a one-off event
Where it belongs
The narrative imperfect belongs to written texts and reports read aloud. Three settings are typical.
Due anni dopo moriva a Parigi, dimenticato da tutti.
Two years later he was to die in Paris, forgotten by everyone.
Biography: the end point of a life
Alle 22 di ieri i carabinieri arrestavano il sospettato.
At 10 p.m. yesterday the carabinieri arrested the suspect.
Police reports and news
Un attimo dopo, la porta si apriva.
A moment later, the door opened.
Novel: the climax of a scene
In biographies, English was to often captures the effect best: the narrator already knows what is coming.
