After joining his ranks, Jiao Yu became one of Zhu Yuanzhang's trusted confidants in the Red Turban Rebellion against the Yuan dynasty. Zhu was impressed with Jiao's knowledge of firearms which he had earlier acquired from Daoren, yet Zhu wanted to test their abilities. Zhu ordered his officer Xu Da to provide a demonstration of their destructive capabilities, and after the display Zhu Yuanzhang was most impressed with their power.
After Jiao Yu joined Zhu Yuanzhang's army, he became one of his closest confidants in the fight against the Yuan dynasty. Zhu was particularly impressed by Jiao's expertise in firearms, which he had learned from Daoren. However, Zhu wanted to see their true potential, so he ordered Xu Da to stage a demonstration of their firepower, and after witnessing it, Zhu Yuanzhang was thoroughly convinced of their effectiveness.