With Pisa in a state of decline, Genoa expanded into Corsica and northern Sardinia. In 1266 Genoese merchants purchased the city of Kaffa from the Golden Horde and went on to establish further trading colonies in the Black Sea and Byzantine Empire. This expansion brought Genoa into further conflict with the powerful city-state of Venice, which also had trade relations in the area. The bitter rivalry escalated into the first of the Venetian–Genoese wars in 1296, at which point Genoa's fleet consisted of 125 galleys. Despite outnumbering the Venetian navy, the Genoese fleet was unable to catch them, and Genoa's merchants suffered greatly during the war. A change came in 1298 when a major engagement was fought in the Adriatic Sea off the coast of Korčula. At the Battle of Curzola, a fleet of 75 Genoese galleys decisively defeated a force of 95 Venetian galleys, destroying or capturing 83 of the enemy ships. However, Genoese casualties were heavy and the city's shipyards were unable to quickly replace the ships lost at Curzola. The conflict ended in a relative stalemate in 1299. Following the war, Genoa dominated the Mediterranean slave trade and the Genoese navy employed thousands of galley slaves as oarsmen. This new policy decreased the cost of maintaining the navy, as rowers no longer had to be paid (as opposed to Venice, which only employed paid rowers), but also decreased the number of men available for boarding parties, as Genoese captains did not trust armed slaves.