Second Goryeo-Khitan War vs Third Goryeo–Khitan War

The Liao army adhered strictly to traditional heavy cavalry assault doctrine, but changing battle conditions revealed their equipment and formations lacked flexibility. Goryeo, however, rapidly learned from the initial pitched battle defeat, shifting from static defense to dynamic hit-and-run and ambush tactics. By adopting an asymmetric doctrine with light infantry and archers in mountainous terrain, they succeeded in neutralizing Liao's superior technology.

By adopting an asymmetric defense doctrine instead of seeking a standard pitched battle, the Goryeo army demonstrated exceptional flexibility. This approach, which moved away from static fortress defense and synchronized ambush, dam attack, and hit-and-run tactics, played a critical role in countering the Liao's steppe warfighting doctrine.

Attrition War

Battle of Annihilation

The Liao Empire correctly identified its center of gravity by targeting the capital Kaesong, achieving strategic success. However, instead of aiming at the enemy's will to resist and supply lines, it pursued a symbolic victory. Goryeo, on the other hand, selected the Liao's critical weakness—extended supply lines—as its center of gravity, concentrating offensive energy there and succeeding in collapsing the enemy. This is a good example of dynamically re-identifying the center of gravity during the course of a war.

The Goryeo Command correctly identified the enemy's center of gravity (its heavy cavalry power and blitzkrieg capability) and built its entire strategy around neutralizing it. Xiao Paiya, however, failed to grasp that the true center of gravity was Goryeo's defensive will and geographical advantage, and mistakenly targeted the capital Kaesong, leading his army to annihilation.

The Liao launched a surprise attack using internal unrest as a pretext, catching the Goryeo court off guard through diplomatic deception. Goryeo, especially during the retreat phase, lured the enemy into traps with misleading routes and irregular troop movements. The flight of the court and the abandonment of the capital served as a delaying tactic by giving the Liao an illusion of victory. While both sides effectively used intelligence and deception elements, Goryeo's asymmetric ruse proved more decisive.

The military deception applied by Goryeo was not focused on feints but on an operational-level ambush and trap strategy. The stunning performance of the dam trap at Heunghwajin, combined with the 'scorched earth' method, paralyzed the Liao army's situational awareness and forced it into a continuous stream of bad decisions.

The Liao army created devastating shock effect in pitched battles through heavy cavalry charges, breaking through Goryeo defensive lines. Yet Goryeo used firepower asymmetrically in mountainous and forested terrain with archery and ambush tactics. While lacking a similar shock weapon like artillery, concentrated volleys of arrows and night raids accelerated the psychological collapse of Liao forces. Goryeo's light troops achieved superiority against heavy-armored cavalry through a synthesis of fire and maneuver.

On the Liao side, the heavily armored Khitan cavalry was the main shock element, but the mountainous, waterlogged terrain chosen by Goryeo prevented its synchronized use. Goryeo, however, combined mass infantry assaults with the environmental shock effect of the dam breach, creating a psychological and physical rupture in the enemy ranks.

The early onset of winter and the inhospitable mountainous terrain drove the heavily equipped Liao army to disaster. Goryeo forces used snowy valleys and forested areas as natural allies, negating enemy numerical superiority through ambushes and night raids. Accustomed to vast plains, the Khitan cavalry doctrine lost maneuverability in the rugged Korean terrain, succumbing to nature.

Goryeo mastered the advantage of 'Heaven and Earth'. At Heunghwajin, they weaponized the river by breaking its dam; they used the mountainous, narrow valleys to destroy the Khitan cavalry's maneuverability. The harsh winter conditions of the Korean peninsula were also a debilitating factor for the invading Khitan army.

The Liao correctly identified Goryeo's internal strife and governance weakness through their spy network, gaining operational timing superiority. Goryeo, on the other hand, discovered the Liao army's advance route and supply difficulties, launching asymmetric attacks especially on retreat lines. While both sides held certain advantages in knowing each other, Goryeo arguably understood its opponent better thanks to local populations and a dispersed intelligence network.

Goryeo flawlessly executed the principle of 'knowing oneself and the enemy' (知彼知己). Gang Gam-chan knew the Khitan army's lethal offensive punch but also its vulnerability in mountainous terrain. Xiao Paiya, conversely, designed his operation underestimating the depth of Goryeo's defense and the local population's will to resist.

At the war's onset, the Liao army advanced rapidly to the capital with a strategic offensive. However, Goryeo successfully redeployed its retreating and resistance forces using interior lines. Particularly, the relocation of the royal court south and coordinated counterattacks by local garrisons trapped Liao on exterior lines and reduced their maneuver speed. While not a Napoleonic unified maneuver, Goryeo's fragmented and flexible operations are a classic example of interior lines.

The Goryeo command leveraged its interior lines advantage to shift forces in a coordinated manner between Heunghwajin, Kwiju, and Kaesong. As the Liao army was drawn into the strategic depth, Goryeo constantly harassed and slowed the enemy with rearguard ambushes and hit-and-run tactics, buying the necessary time for the final encirclement.

Initially, Liao's overwhelming cavalry charges and Gang Jo's execution caused shock and moral collapse in Goryeo ranks. But the loss of the capital and the court's flight paradoxically fueled the people's will to resist. Clausewitz's friction came into play: as the occupying army began suffering heavy losses and harsh winter conditions set in, the fighting spirit of Liao soldiers broke, whereas the moral multiplier of Goryeo troops defending their homeland soared.

For Goryeo, the war became a defense of the homeland, with the population supporting the army with a powerful 'will to victory'. In contrast, for the Liao army, the Clausewitzian 'friction' generated by logistical collapse and relentless harassment rapidly eroded its initially high morale; the inability to celebrate Nawruz was a particularly significant factor in their spiritual collapse.

Goryeo could not recruit allies pre-war through diplomatic maneuvers, but during the war, the psychological will to resist shook Liao's occupation goals. After the sacking of Kaesong, the populace's total resistance broke the invader's moral superiority. Conversely, the Liao gained a political advantage by using Gang Jo's rebellion as casus belli, yet ultimately failed to achieve the goal of winning without fighting as they could not extract final diplomatic concessions.

At the strategic level, Goryeo drove the invasion into a logistical dead end before it truly began through the 'scorched earth' (Cheongya) method. The Liao army started to struggle with thirst and hunger before even reaching Kaesong, forcing a mandatory retreat that created the conditions for 'winning without fighting'.