As the international order in the East Asia shook due to the weakening of the Yuan’s power, Red Turban Army, a rebellion group of farmers of China, invaded Goryeo twice. Since the Goryeo’s military power was weakened during the Yuan’s intervention period and the military forces were dispersed due to the intrusion of the Japanese pirates and the preparations against the Jurchen people in the Northeast area, Goryeo could not fight well from the beginning at its 1st invasion in 8th year of King Gongmin, Therefore, while the invaders were being disturbed or blocked in the northwestern region, the Goryeo government issued a military policy to gather the army. The person responsible for this mission was Ahn-Woo. Ahn-Woo defeated the Red Turban Army several times in the Cheolju and the Cheong River. So, the Red Turban Army bypassed the Cheong River, went to the back of the Ahn-Woo’s army for ambush, and tried to lure the Ahn-Woo’s army. The Ahn-Woo’s army was greatly defeated by the ambush operation. The Ahn-Woo’s army had to retreat to Jeongju. Since the Goryeo army could not complete the gathering yet, Goryeo had no choice but to give up Seogyeong and it was captured by the Red Turban Army. After the fall of Seogyeong, Goryeo gathered all its troops and attacked Red Turban Army. At this time, under the leaderships and sacrifices of the commanders, including Ahn-Woo, Goryeo led the battle to victory, and the Red Turban Army, which had had originally 40,000 soldiers, went back only with 300 survivors.
The second invasion of the Red Turban Army was in the 10th year of King Gongmin. As the problems faced by the first invasion were not solved yet, and the damage during the first invasion was not recovered, Goryeo’s situation was more disadvantageous than the first invasion. Moreover, the number of Red Turban Army was 200,000, or five times the number at the first invasions. So, the Goryeo government decided to use cheongya tactics, setting up the wooden barriers on Jeolryeong of Hwanghae Province, and moving people and grain to this place. This was to give up the area of Pyeongan-do including Seogyeong. And, as at the first invasion, the Goryeo Army led by Ahn-Woo began to open a guerrilla tactics in the intrusion routes of Red Turban Army.
At the 2nd invasion, the Red Turban Army evade the area where they had been defeated at the 1st invasion and moved to Sakju on the inland to attack Guiju and Muju. The Goryeo Army of Ahn-Woo accomplished many achievements by launching a guerrilla warfare on the way to the Red Turban Army's invasion route. In the end, however, they were defeated in Anju due to the small number of soldiers, and retreated to Jeolryeong.
While the Goryeo Army gathered at Jeolryeong, the Red Turban Army of 10,000 soldiers attached them at night. The Goryeo Army, which was raided, was greatly defeated. the Goryeo government, which thought that it was difficult to block the invasion of Red Turban Army, abandoned Gaegyeong the capital city and evacuated. After then, Goryeo succeeded in gathering 200,000 soldiers near Gaegyeong, and spied on the defensive state of the Red Turban Army. Detecting that the defense of the Sungin Gate where the enemy's main power was residing, they began to attack that area intensively and made a victory. In the end, the Red Turban Army was greatly defeated, and only about 100,000 Red Turban Army could cross back the Aprok River.
Goryeo Army was a minority when compared to the Red Turban Army, but another reason why they were defeated in the first and second battles with the Red Turban Army was that they could not catch the surprise attack or detoured movement of enemies due to the failure of vigilance and ambushed by them. On the other hand, the reason why Goryeo Army could won the war was that they detected the Red Turban Army’s weakness and executed the battle plans, taking advantage of it. In other words, the most basic matters such as ambush and surprise attack frequently determined the victory and defeat of the battles. In addition to this, it can be seen that the leadership, sacrifice spirit, and bravery of Goryeo Army commanders including Ahn-Woo were the main factors of the battle victory.