Wu Sangui has been looking forward to opening up a new battlefield in the northwest since the beginning of the war. He pinned this hope on his old subordinates, Shaanxi Taishou Wang and Gansu Taishou, and sent them as special envoys to persuade them to start fighting. The king handed him over to the court and the court put him to death. Wu Sangui had given up, but Moro, who was running in Shaanxi, single-handedly defeated Wang. In December of the 13th year of Kangxi (1674), Wang Zaining killed Moro and rose up. In the 14th year of Kangxi (1675), Wang captured Lanzhou, an important town in the northwest, and the northwest shook.

In such a good situation, Wu Sangui made a strategic mistake. He drank horses from the Yangtze River and should have drunk Huanglong, but Wu Sangui has never been to the Yangtze River. He stopped in Songzi for more than three months and lost a good opportunity in vain. Liu Xuanchu, the counselor of Wu Sangui, wrote a letter at an important time, urging him to cross the river to the north, but he was indifferent and kept watching in an attempt to rule the Yangtze River with the Qing court. If he invaded the north at this time, the mountains and rivers of the Qing Dynasty might change color, but he stopped. Lack of enterprising spirit is an important reason for Wu Sangui's ultimate failure, and history is so ruthless.

Because of Wu Sangui's hesitation, he failed to seize this opportunity, but Emperor Kangxi, on the contrary, mobilized the military forces of the whole country and came to Wu Sangui. Kangxi first stripped Wu Sangui of his title, and then executed Wu Sangui's son Wu and his son who stayed in Beijing. By April of the 14th year of Kangxi (1675), Emperor Kangxi had organized the Tenth Route Army to suppress Wu Sangui's army and even recruited Mongolian soldiers to the front, with a total strength of more than 200,000. The main forces of the two sides are in Hunan, Wu Jun is in Yuezhou, and the base camp of the Qing army is in Jingzhou on the other side. They have been confronting each other.

Emperor Kangxi adopted the policy of divide and rule, and the king in the northwest was defeated first. The Qing army first captured Qin Zhou, and the company commander Chen Wance surrendered. Then surrounded Lanzhou and Changgong. Lanzhou and Lanzhou were successively breached, and the Qing army surrounded Pingliang, the base of Wang. Kangxi sent Tu Hai, a college student, as General Fuyuan to Pingliang to direct the battle. The Qing army paid a huge price to seize the commanding heights outside the city-Hushandun, and Pingliang City lost its barrier. Wang surrendered in June in the 15th year of Kangxi (1676) and pacified the northwest. The victory of the northwest battlefield made Kangxi eliminate elbows and armpits, and finally he could deploy northwest forces to deal with Wu Sangui, so Wu Sangui's failure was doomed.