Portuguese foreign policy promoted the interests of Lisbon: trade and cooperation agreements were signed with the commercial city-states of Venice (accord of 1392), Genoa (1398), Pisa and Florence, whose merchants had already formed communities in the city, and many of whom were naturalised and married into the Portuguese nobility. Ceuta on the north African coast was captured by the Portuguese in 1415, giving Lisbon's merchants a base from which to attack Saracen pirates and better local control of the Mediterranean trade that passed through the Strait of Gibraltar, as well as the importation of Moroccan wheat at the best prices. Moreover, at this time Ceuta received caravans bearing gold and ivory, a trade Lisbon wanted to dominate, and it was feared that its Castilian rivals in Seville or the Aragonese of Barcelona might seize the outpost. A renewed alliance with England, one of its most important trade partners, was pursued.