Paekche–Tang War vs Silla–Tang War

Tang's flexible doctrine combining amphibious and land warfare rendered Paekche's static wall defenses obsolete. Silla maintained the initiative with rapid transit and encirclement tactics in rugged terrain. Paekche initially shifted to guerrilla resistance but lost flexibility after maritime isolation; Yamato's outdated naval doctrine prevented adaptation.

Silla adopted a dynamic attrition doctrine rather than static defense, effectively combining fort defenses with guerrilla offensives. Tang adhered to traditional Chinese expedition doctrine (heavy infantry and siege techniques) and failed to adapt sufficiently to changing conditions.

Battle of Annihilation

Attrition War

The Tang-Silla alliance correctly identified and struck Paekche's center of gravity — the political and military capital Sabi — through a joint offensive. Coordinated naval and land operations rapidly collapsed the enemy's core. Paekche failed to mass its defense forces and only offered a tactical delay with Gyebaek's last stand.

Tang's true center of gravity was the Tibetan front; insufficient force allocation to the east created strategic ambiguity. Silla directed its operational center of gravity at Tang garrisons in former Baekje territory, successfully collapsing Tang resistance there.

The Tang fleet's deceptive routing and choice of landing site achieved strategic surprise. Silla's unexpected attack through a mountain pass further divided Paekche's defense. Yamato's naval expedition suffered from intelligence gaps and tactical deception, leading to its entrapment at Baekgang.

Silla used diplomatic deception, declaring loyalty to Tang before launching surprise attacks. It also employed Goguryeo and Baekje insurgents to distract Tang, preventing Tang from concentrating its main forces on the front.

The Tang fleet's sudden attack at the Geum River mouth shattered Paekche's defensive lines, and the amphibious assault paralyzed the enemy's central command. At Hwangsanbeol, Silla cavalry's swift shock charge overwhelmed outnumbered Paekche infantry. At Baekgang, coordinated arrow and incendiary attacks from Tang warships dispersed the Yamato fleet on the first day, seizing psychological dominance.

Silla avoided large pitched battles to absorb Tang's superior artillery and cavalry shock. Instead, fort defenses and night raids neutralized Tang's firepower. At sea, the Silla navy broke Tang's amphibious shock capability through coastal defense and estuary ambushes.

Favorable wind and current conditions during the 660 campaign allowed the Tang fleet a swift and safe crossing of the Yellow Sea. Although Paekche's capital Sabi lay inland on the Geum River, defenses at the river mouth could not stop Tang's naval power. At Baekgang, the narrow river mouth constrained Yamato's fleet maneuverability, enhancing Tang's tactical advantage. The mountainous terrain slowed Silla's eastern advance but reduced Paekche's defense depth.

Korea's mountainous terrain and harsh winters offered natural advantages to Silla's defensive tactics. Tang's campaign seasons were limited by frozen rivers and impassable mountains; Silla turned this difficult terrain into a force multiplier with interior-line maneuvers.

Tang and Silla shared comprehensive intelligence on each other's military status and enemy vulnerabilities. Silla's informant network in the Paekche court and Tang reconnaissance reports revealed critical weak points. Paekche was unaware of Tang's mobilization, and Yamato's long-range intelligence efforts were inadequate.

Silla gathered critical intelligence via students and merchants in the Tang court; for example, prior warning of the 670 invasion plans enabled organized defense. Tang failed to adequately analyze Silla's internal dynamics, especially coalition cohesion.

Tang forces disrupted Paekche's defensive order with a rapid amphibious landing and advanced quickly toward the interior. Silla's army, crossing mountain passes, executed a simultaneous offensive that trapped the enemy. Paekche lost all maneuver space around the capital. During the resistance, late-arriving Yamato reinforcements failed to provide the necessary freedom of movement for interior defense.

Silla leveraged interior lines to rapidly shift forces from one front to another. Tang's slow, overseas movements on exterior lines were ineffective against Silla's maneuverability. The swift capture of forts in the Baekje region exemplified this flexibility.

The quick capture of the capital by the Tang army shocked Paekche troops, leading to mass surrenders. General Gyebaek's death broke Paekche's organized resistance; King Uija's surrender extinguished the people's will to fight. Conversely, Tang's harsh occupation initially sparked popular resistance, but the decisive defeat at Baekgang and Prince Buyeo Pung's flight dashed the last hopes.

On Silla's side, a sense of national resistance against a foreign power kept morale high. Tang soldiers suffered from an unclear strategy and war-weariness away from home. Silla's common cause as coalition leader cemented psychological superiority.

The Tang Empire diplomatically isolated Paekche by allying with Silla and applied psychological pressure before the war. Emperor Gaozong's repeated warning edicts caused divisions within the Paekche court, weakening resistance will as some aristocrats surrendered. In contrast, Paekche failed to build a deterrent despite its alliances with Goguryeo and Yamato.

Silla gained strategic advantage without fighting by deepening Tang's internal political pressures (Tibetan threat, court intrigues) through diplomatic maneuvers. The tributary mission in 675 successfully diverted Tang's attention westwards.