Adriatic, e.g. Ancona (839). In 840 the treachery of the Gastald Pando handed over to them Bari, where they fixed themselves permanently, and it was the Saracens of Bari whom Radelchis of Benevento employed as auxiliaries during his struggle with Siconolf of Salerno. Other pirate crews attempted the siege of Naples, but the city offered a determined resistance, and its duke, Sergius, at the head of a fleet collected from the Campanian ports, won the naval victory of Licosa over the invaders in 846. Repulsed from the Campanian shores, the pirates fell upon the coast nearest to Rome. In order to keep them out of the Tiber, Pope Gregory IV had built a fortress at its mouth. This did not prevent the pirates from landing on the right bank of the river and even pushing their ravages as far as the gates of Rome. Unable to force their way in, they sacked the basilica of St Peter, which was then outside the walls, profaning the tomb of the Prince of the Apostles.
This sacrilege created a profound sensation throughout Christendom. It was, indeed, related that a tempest destroyed the invaders with the precious booty with which they were laden. But the truth appears to be that Louis II, as he was advancing to the rescue of the city, met with a check, and that the Saracens retired unmolested with their spoil. A great expedition organised against them in the spring of the next year (847) by Lothar I and Louis II had no important results. Louis, however, took advantage of being in the south of Italy to put an end by treaty to the contest between Radelchis and Siconolf, definitively separating by a precise frontier line the two principalities of Benevento and Salerno. The Roman suburbs had arisen from their ruins, and Pope Leo IV (847-8) had built a wall round the basilica of St Peter and the quarter on the right bank of the Tiber, enclosing what became "the Leonine City." In 851-2 the Lombards again appealed to Louis II. The latter delivered Benevento from the body of Saracens which had settled down there, but being badly supported by his allies, he was unable to take Bari, the Muslim garrison of which, as soon as the Frankish army had withdrawn, re-commenced its devastating raids into the surrounding country. It was at this time that the Saracens pillaged the famous abbeys of Monte Cassino and St Vincent of Volturno. In 867 the Emperor made a fresh expedition against them, and laid siege to Bari. But it was impossible to reduce the town without the help of a squadron to blockade it from the sea. Louis II, therefore, attempted to secure the aid of the Greek fleet by an alliance with the Basileus, arranging for the marriage of his daughter Ermengarde with the son of Basil, the Eastern Emperor. A Greek fleet did, indeed, appear off Bari, but the marriage not having taken place, it drew off. Louis was not discouraged, and made a general appeal to his subjects in the maritime provinces, even to the half-subjected Slavs to the north of the Adriatic. After many vicissitudes, the town was carried by assault (2 February 871). But the Lombards of Benevento cordially detested
