In late June 1333, a samurai lord named Nitta Yoshisada (新田義貞, Nitta Yoshisada) stood at one of the great decision points of Japanese history — at the edge of the sea, in full armor, with no way forward. He was thirty-two years old, a lord of the Minamoto (源氏, Minamoto-shi) lineage from Kozuke Province (上野国, Kōzuke no kuni), and he had spent weeks answering Emperor Go-Daigo's (後醍醐天皇, Go-Daigo Tennō) call to destroy the Hojo regency (北条氏, Hōjō-shi). The Hojo clan did not rule Japan as its official government — that title belonged to the Kamakura shogunate (鎌倉幕府, Kamakura bakufu) — but for generations they had controlled it through the office of regent (執権, shikken), reducing the shogun to a figurehead. Go-Daigo wanted them gone. Yoshisada had come to do it.

Kamakura (鎌倉, Kamakura) was not an easy city to attack. It sat in a natural fortress: surrounded on three sides by steep forested ridgelines, with only a handful of narrow passes — the kiridoshi (切通し, kiridōshi) — connecting it to the outside world. On the south, the sea formed the fourth wall. The Hojo defenders had fortified every mountain pass; Yoshisada's forces had fought through several of them and taken heavy casualties. The coastal approach below Inamuragasaki (稲村ヶ崎, Inamuragasaki) Cape, running along the edge of Sagami Bay (相模湾, Sagami-wan), appeared to offer another way in — but at normal tide, the sea covered the beach entirely. There was no path.

What happened next exists in the space between history and legend, recorded in the Taiheiki (太平記, Taiheiki), the great fourteenth-century war chronicle that mixed documented events with vivid literary embellishment. According to the Taiheiki, Yoshisada walked into the surf in full battle armor, drew his gold-mounted tachi (太刀, tachi) sword — the defining possession of a samurai warrior, the object in which his identity and spirit were said to reside — and cast it into the sea as an offering. In some versions of the text, he prayed to Ryūjin (竜神, Ryūjin), the dragon god of the sea believed to dwell in a great underwater palace and govern the tides. In others, he prayed to Amaterasu (天照大神, Amaterasu Ōmikami), the sun goddess and divine ancestor of the imperial line. The sword sank. The tide fell. The beach around the cape was exposed. Yoshisada's army marched through.

The exact Gregorian date of this episode is genuinely uncertain. The Taiheiki gives the 21st day of the 5th month of Genko 3 (元弘3年, Genkō 3-nen), and different conversion methods place the corresponding Gregorian date anywhere from late June to mid-July 1333. A commemorative stele at the site gives a different date. The astronomer Kiyohiko Ogawa argued from tidal calculations that July 8 was the most plausible date for a significant tidal exposure. The scholarly consensus holds that this entry is properly understood as a legend-date framing — Yoshisada's approach through Inamuragasaki occurred as summer began in 1333, and the precise calendar correspondence cannot be pinned down with certainty.

What is not in doubt is what the tidal route made possible. Yoshisada's forces entered Kamakura from the south — the one direction the defenders had treated as impassable and therefore left under-defended. The city fell quickly once the outer defenses were breached. The Hojo regent and the senior members of the Hojo clan retreated to Toshoji (東勝寺, Tōshōji), the family temple, where they committed ritual suicide together. More than 870 people died in and around the temple — the Hojo clan, their retainers, and followers who had served the regency for generations, choosing death over surrender. The Kamakura shogunate, which had governed Japan since 1185 — 148 years — ended in a single afternoon.

The image of Yoshisada at the water's edge became one of the most reproduced moments in Japanese warrior art. The act was remarkable in its symbolism: the sword is the samurai's soul, the object that defines his identity and status, the thing he is least supposed to surrender. To throw it into the sea was not defeat — it was total submission to something larger than himself, a wager of everything he was on a prayer. The Walters Art Museum in Baltimore holds a tsuba (鍔, tsuba) sword guard depicting the scene. Harvard Art Museums holds a woodblock print. A monument marks Inamuragasaki today; it is still visited by tourists who walk the same stretch of Sagami Bay shore.

The end of the Kamakura shogunate did not bring the peace Yoshisada and Go-Daigo hoped for. The emperor's Kemmu Restoration (建武の新政, Kenmu no Shinsei) attempted to restore direct imperial rule, distributing the Hojo lands among loyalists — but the settlement satisfied almost no one. Within three years, the warrior lord Ashikaga Takauji (足利尊氏, Ashikaga Takauji), who had fought against the Hojo, turned against Go-Daigo and established his own shogunate. Yoshisada remained loyal to the emperor to the end; he died in battle in 1338, never seeing the new order stabilize. The tide had opened Kamakura for him. What came after was beyond anyone's control.