From African Samurai, by Geoffrey Girard and Thomas Lockley (Hanover Square, 2019), Kindle pp. 310-311:
Chinese pirate crews in the South China Seas, an area which no state power adequately controlled and where it was often in minor rulers’ interests to turn a blind eye for their own financial benefit, often employed Africans who had escaped from slavery or gone it alone. An example, though shortly after Yasuke’s time in the 1620s, was the Chinese pirate, smuggler and merchant, Zheng Zhilong.
Zheng had a large African bodyguard corps, more than three hundred men at its peak. The bodyguards were recruited from various places, but most entered his service via Macao, the Portuguese enclave in southern China, and many were escaped slaves. They could also have been men freed in reward for their part in the successful defense of Macao against the Dutch in 1622.
In this battle, an attempt by the Dutch to wrest control of the inter-Asian trade from the Portuguese, Macao found itself virtually defenseless as the Dutch attacked when most of the Portuguese merchant militia were away on trading missions in China. In a desperate bid to defend the outpost, all African slaves—a large group who did most of the manual labor in the colony—were granted their freedom, and as much alcohol as they could drink, in exchange for fighting in the city’s defense. These drunken, newly freed men and women were wildly successful in destroying the Dutch, and their mercenary Japanese and Thai troops, despite being heavily outnumbered. The Africans charged the Dutch musket fire fearlessly and gave no quarter; and as it was the feast of John the Baptist, allegedly celebrated by removing heretic Protestant heads from their bodies. The former slaves, having been released from their bondage, would have been searching for better employment (and quickly), and pirates such as Zheng Zhilong could provide this.
Zheng had lived much of his life in Japan, where he was safe from Chinese government authority and could take advantage of Japanese and European trade and smuggling opportunities. At the height of his power, his fleet was estimated at up to a thousand ships and controlled almost all interactions in the South China Sea.