Some of the most important trade routes began at Canton and Macau in Qing Dynasty China . Early in each year a large convoy known as the " China Fleet " , composed of large East Indiaman merchant ships in the employ of the British East India Company , sailed westwards to Europe from Macau laden with tea and other commercial cargo . This convoy was economically significant to Britain : one convoy in 1804 was valued at over £ 8 million ( the equivalent of £ 600 @,@ 000 @,@ 000 as of 2016 ) . In January 1797 the convoy had been attacked by the French squadron in the East Indies , comprising six frigates commanded by Contre @-@ amiral Pierre César Charles de Sercey . In the ensuing Bali Strait Incident the commander deceived Sercey into believing that the unescorted convoy contained disguised ships of the line and the French admiral retreated , only learning of his error on his return to Île de France . It was considerable concern in India that Sercey might try again in 1798 , or that the Spanish , who maintained a powerful squadron at Cavite , might make an attempt of their own .