Coalition Invasion & Battle of Sai (Hundred Days War)

A coalition of six states invades Qin in the largest military operation in the series, breaking through the Kankoku Pass and forcing the entire kingdom into a defensive war that culminates in the hundred-day siege of the city of Sai with the king himself on the wall.

The Coalition Invasion is widely considered the single greatest arc Hara has written and one of the defining war arcs in modern manga. A coalition of the six remaining states — Zhao, Wei, Han, Chu, Yan, and Qi — invades Qin through the Kankoku Pass, a mountain choke-point whose loss would expose the road to the capital and end the war. The arc opens with one of the most cinematic mass-army sequences in the series and unfolds as a sustained meditation on what national-scale defensive war does to soldiers, commanders, and the political institutions that send them into the field. The arc is told across two interwoven theaters. The northern theater at the Kankoku Pass features the Qin defensive line under Generals Mou Bu, Tou, Duke Hyou and the recently elevated Ou Sen, holding against the combined armies of multiple states under the supreme command of Coalition strategist Kakurirou. The southern theater follows the Hi Shin Unit and elements of the Qin army to the city of Sai, the secondary capital that the Chu prime minister Riboku has revealed will be attacked by a parallel Chu force in a feint designed to flank the entire Qin defense. King Ying Zheng himself takes personal command of the Sai defense and stands on the city's walls for one hundred days alongside Shin and the surviving units, holding the city against forces that outnumber them at every measurable level. The Hundred Days War of Sai is the arc's emotional and structural climax. Hara devotes hundreds of chapters to the day-by-day collapse of the city's defenses, the deaths of named officers and ordinary soldiers in equal proportion, and the moment when Ying Zheng picks up a sword on the wall not as a symbol but as a working soldier. The defense holds. The Coalition fractures along its political seams. Qin survives. The arc closes with the king of Qin returning to the capital with the formal recognition of every soldier who fought at Sai that the man who stood with them on the wall is the figure they will follow into a unification war.