Pierleoni led the defence of the city against Pope Lucius II's assault in 1145, where Lucius himself was killed. However, Pierleoni was unable to maintain order in the city despite his overtures of negotiations with Lucius—demanding the pope renounce secular authority and live as a common priest before being allowed reentry into the city, —he was deposed by the people who invited Pope Eugene III, Lucius' successor, back.
Pierleoni headed the city's defense against Pope Lucius II's attack in 1145, where Lucius himself was slain. However, Pierleoni failed to maintain order in the city despite his attempts at dialogue with Lucius—requesting the pope relinquish secular power and live as a common priest before being permitted reentry into the city, —he was ousted by the people who invited Pope Eugene III, Lucius' successor, back.