 Complete the following phrase:  The Saracens soon became too dangerous to keep as friends and Naples was forced to ally with Amalfi, Gaeta, and Sorrento, its practically independent underlings, and make war on the Muslims. The Christians forced them out of Ponza and defended Rome in 846, though the Vatican was sacked. In 849, Sergius led his fleet alongside that of Gaeta and the Vatican in the successful 