Wikipedia
The hongyipao was a smoothbore muzzle-loading culverin introduced to China and Korea from the Portuguese colony of Macau in the early 17th century. The term "red barbarian cannon" derives from the weapons' supposed Dutch origins, as the Dutch were called "red haired barbarians" in Chinese. However, the cannons were originally produced by the Portuguese at Macau, with the exception of two cannons dredged up from a Dutch ship in 1621. The Dutch ship may have been in fact an English ship and the cannons had English coats of arms. The English ship Unicorn sank near Macau. After the Ming dynasty suffered a series of defeats against the Later Jin dynasty, they contacted the Portuguese to have iron cannons made for them. Attempts were made to bring Portuguese gunners to the north as well, but they were repeatedly turned away because Chinese officials harbored suspicions against them.
Several of the officials who supported the use of the new technology were Christians, among them Xu Guangqi (a convert of the Italian Jesuit Matteo Ricci), and Sun Yuanhua, the governor of Shandong. The Tianqi Emperor asked a German Jesuit, Father Johann Adam Schall von Bell, to establish a foundry in Beijing to cast the new cannons. The first pieces produced there could throw a forty-pound shot. In 1623 some hongyipao were deployed to China's northern frontier at Sun Yuanhua's request under generals such as Sun Chengzong and Yuan Chonghuan. They were used to repel Nurhaci at the Battle of Ningyuan in 1626. After the Later Jin captured a Ming artillery unit at Yongping in 1629, they too began production of the hongyipao. The manufacture and use of the hongyipao within the Later Jin Banner armies were carried out by Han Chinese defectors called ujen coohai (heavy troops). The Jurchen forces did not manufacture nor wield the guns themselves. The Later Jin forces under Nurhaci's son Hong Taiji, used these cannons along with the "generalissimo" cannons (also of European design) to great effect at the Battle of Dalinghe in 1631. After the later Jin became the Qing and the Jurchens and Han Chinese defectors were reorganized into the Eight Banners, the Han Chinese Banners continued to exclusively wield the gunpowder weapons like artillery and muskets while the Manchu Banners did not use them. Han Chinese Bannermen wielding artillery helped the Qing reduce Ming fortresses and cities under siege.
The Folangji was the first western designed gun reverse engineered by the Chinese after the Chinese defeated the Portuguese at the Battle of Xicaowan in 1521 and captured their guns as war booty.