Though Havana, which had become the third-largest city in the Americas, was to enter an era of sustained development and increasing ties with North America during this period, the British occupation of the city proved short-lived. Pressure from London to sugar merchants, fearing a decline in sugar prices, forced negotiations with the Spanish over the captured territories. Less than a year after Britain captured Havana, it signed the 1763 Treaty of Paris together with France and Spain, ending the Seven Years' War. The treaty gave Britain Florida in exchange for Cuba. Cubans constituted one of the many diverse units which fought alongside Spanish forces during the conquest of British West Florida (1779–81).