 Complete the following phrase:  Several Ming officials who supported the use of the new technology were Christian converts of the Jesuit mission, such as the influential minister Xu Guangqi and Sun Yuanhua in Shandong. The Tianqi Emperor asked a German Jesuit, 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 Chinas northern frontier at Suns 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 . The manufacture and use of the hongyipao within the Later Jin Banner armies were carried out by Han Chinese defectors called heavy troops. The Jurchen forces did not manufacture nor wield the guns themselves. The Later Jin army under Nurhacis son Hong Taiji used these cannons along with the generalissimo cannons also of European design to great effect at the 