Taking advantage of the weakened power of Yuan, the Red Turbans, a powerful Chinese brigand force, arose in northern China. They invaded various territories of the Yuan. One of these bands fled into the territories of Goryeo upon attack from the Yuan. At one point, Gaegyeong was seized by the Red Turban invaders, and King Gongmin was forced to flee, but Goryo forces soon drove them away. However, it was the raids of the Japanese marauders (waegu) that put Goryeo in a crisis. The fallen, low-class warriors of Japan, came by sea, landed along the Goryeo coast and launched numerous raids. Due to the rampant raids by the waegu, taxes could no longer be brought to the capital, causing it to face economic difficulties. The coastal regions became devastated and even the inland areas far away from the coasts suffered great damage. Goryeo exerted its strength in suppressing the waegu, and erected defensive facilities. Choi Mu-seon achieved outstanding success in destroying 500 Japanese ships with the gunpower weapons he produced. The military commanders, including Choi Yeong and Yi Seong-gye, who accomplished major victories in destroying the Red Turbans and the Japanese marauders, won the trust of the king and the peasantry, and their influences mounted.