Innocent II against king Roger II of Sicily. Amalfi, one of the maritime republics (though already declining under Norman rule), was conquered on August 6, 1136; the Pisans destroyed the ships in the port, assaulted the castles in the surrounding areas, and drove back an army sent by Roger from Aversa. This victory brought Pisa to the peak of its power and to a standing equal to Venice. Two years later, its soldiers sacked Salerno. In the following years, Pisa was one of the staunchest supporters of the Ghibelline party. This was much appreciated by Frederick I. He issued in 1162 and 1165 two important documents, with these grants: Apart from the jurisdiction over the Pisan countryside, the Pisans were granted freedom of trade in the whole empire, the coast from Civitavecchia to Portovenere, a half of Palermo, Messina, Salerno and Naples, the whole of Gaeta, Mazara, and Trapani, and a street with houses for its merchants in every city of the Kingdom of Sicily. Some of these grants were later confirmed by Henry VI, Otto IV, and Frederick II. They marked the apex of Pisa's power, but also spurred the resentment of cities such as Lucca, Massa, Volterra, and Florence, thwarting their aim to expand towards the sea. The clash with Lucca also concerned the possession of the castle of Montignoso and mainly the control of the , the main trade route between Rome and France. Last, but not least, such a sudden and large increase of power by Pisa could only lead to another war with Genoa. Genoa had acquired a largely dominant position in the markets of southern France. The war presumably began in 1165 on the Rhône, when an attack on a convoy, directed to some Pisan trade centres on the river, by the Genoese and their ally, the count of Toulouse, failed. Pisa, though, was allied to Provence. The war continued until 1175 without significant victories. Another point of attrition was Sicily, where both the cities had privileges granted by Henry VI. In 1192, Pisa managed to conquer Messina. This episode was followed by a series of battles culminating in the Genoese conquest of Syracuse in 1204. Later, the trading posts in Sicily were lost when the new Pope Innocent III, though removing the excommunication cast over Pisa by his predecessor Celestine III, allied himself with the Guelph League of Tuscany, led by Florence. Soon,