The pomerium was the sacred boundary of Rome, a religious and political line that marked the city as more than a physical settlement.
Historical Significance
The boundary mattered because military command and civic authority were not identical inside and outside Rome. To bring armed force against the city was therefore not only political rebellion but an assault on sacred order.
In Chapter V
The chapter uses the pomerium to explain why Sulla’s action was felt as a rupture deeper than ordinary illegality.