By the summer of 1183, the 源平合戦 (Genpei Kassen) — the Genpei War — had been grinding for two years, and the 平家 (Taira) clan still held the dominant position. They controlled Kyoto, held the young emperor, and commanded the resources of the imperial court. The 源氏 (Minamoto) resistance was scattered across the provinces, dangerous in pockets but not yet a unified threat. The 平家 (Taira) strategy was simple: concentrate force, destroy each Minamoto leader in turn, and end the war before a coherent opposition could form.

源義仲 (Minamoto no Yoshinaka) — 木曽義仲 (Kiso Yoshinaka), as he was commonly known, raised in the mountains of 信濃 (Shinano) Province — had been building a formidable army in the north. The 平家 (Taira) dispatched a force under 平維盛 (Taira no Koremori), the grandson of 平清盛 (Taira no Kiyomori) himself, to eliminate him. The 平家物語 (Heike Monogatari), the great chronicle of the war, gives the 平家 (Taira) army a strength of 100,000 — a figure that almost certainly reflects the literary tradition of making great battles sound suitably vast. Modern historians estimate the actual force in the tens of thousands. Whatever its exact size, it was substantially larger than what 義仲 (Yoshinaka) could field, and it moved with the confidence of superior numbers toward a decisive engagement.

The two armies met at 倶利伽羅峠 (Kurikara-toge), a narrow mountain pass on the border of 越中 (Etchu) Province — now 富山県 (Toyama Prefecture) — and 加賀 (Kaga) Province — now 石川県 (Ishikawa Prefecture). The pass was a natural bottleneck: steep slopes on both sides, a narrow track along the ridge, and a deep ravine below. For an army marching in column it was exactly the kind of terrain where numbers stopped being an advantage and started being a problem. The men at the front had no room to maneuver; the men at the back could not see what was happening ahead.

義仲 (Yoshinaka) understood this terrain. He also understood something about how armies think when they believe they are winning. He spent the entire day of the battle in what amounted to theatrical performance: his forces engaged the 平家 (Taira) front in steady skirmishing, pressing just enough to keep them occupied and confident, pulling back just enough to prevent a decisive breach. All day the 平家 (Taira) commanders believed they faced his main strength. All day, 義仲 (Yoshinaka) was quietly moving thousands of soldiers around both flanks of the pass, through the forested slopes above the ridge, out of sight and out of sound.

The 奇計 (kikei) — the unorthodox stratagem — had been borrowed from a Chinese military text. Around 280 BCE, the general Tian Dan of the state of Qi had used a herd of oxen with fire tied to their tails to break a siege and destroy the army of the state of Yan. The method had been recorded, studied, and preserved for roughly 1,460 years by the time 義仲 (Yoshinaka) chose to deploy it in a mountain pass in central Japan. He rounded up a herd of oxen, tied lit torches to their horns, and as darkness fell he drove them down the narrow pass directly into the 平家 (Taira) lines.

The effect was precisely what the ancient Chinese text had described. Burning animals in total darkness are unstoppable. Their panic is genuine and absolute; they do not respond to commands or to the presence of armed men. The torches tied to their horns created moving, unpredictable fire across the entire width of the pass. The 平家 (Taira) formation, already crowded and unable to deploy properly in the narrow terrain, came apart in an instant. At exactly that moment, 義仲 (Yoshinaka)'s flanking forces attacked from both sides simultaneously, and his central force charged down the north slope. The 平家 (Taira) army was struck from three directions in the dark, in a narrow gorge, by troops they had not known were there.

The 平家物語 (Heike Monogatari) describes the aftermath with characteristic poetry: thousands of warriors plunging from the mountain paths into the ravine below, the gorge filling with bodies, the sound of the army's collapse echoing through the pass. The exact numbers cannot be confirmed from the literary source, but the military outcome was unambiguous. The 平家 (Taira) retreated toward Kyoto in disorder. They had lost the initiative permanently. Within months they would be driven from the capital entirely.

The battle's Gregorian date carries a small uncertainty — sources most commonly give it as approximately early June 1183, with the original Japanese date being the 11th day of the 5th month of 寿永2年 (Juei 2). 義仲 (Yoshinaka) marched on Kyoto after his victory, entering the capital in triumph — the first Minamoto to do so. What followed was more complicated, and ended badly. But at 倶利伽羅峠 (Kurikara-toge), he was 29 years old and at the peak of his art.