Born as Prince Oama, a son of Emperor Jomei, within the Asuka-period court centered around Yamato. He grew up among powerful Soga-linked factions and competing princes, learning the politics of succession early.

The Isshi Incident toppled Soga no Iruka and reshaped power under Naka no Oe and Nakatomi no Kamatari. The young prince saw how coups and alliances could redirect the throne, shaping his later caution and resolve.

As Baekje fell and Tang-Silla power surged in Korea, the Yamato court mobilized resources and diplomacy. Prince Oama operated within elite circles responding to foreign threats, reinforcing the need for centralized authority.

Yamato forces were crushed at the Battle of Baekgang, ending hopes of restoring Baekje and exposing Japan’s vulnerability. The defeat intensified domestic reforms and military preparedness, conditions that framed his later state-building.

Emperor Tenji shifted the political center to Omi-otsu Palace, seeking tighter administration after continental alarms. Prince Oama’s position at court placed him close to succession politics as Tenji’s health declined.

As Tenji elevated Prince Otomo, rival blocs formed around court offices and provincial ties. Oama navigated dangerous rivalries and prepared supporters in the east, anticipating that a disputed succession could turn violent.

After Emperor Tenji’s death, Oama left the Otsu court and entered seclusion at Yoshino, outwardly renouncing ambitions. The move reduced immediate suspicion while allowing him to cultivate allies beyond the capital’s scrutiny.

In 672, Oama launched a bid for power, rallying eastern clans and provincial officials against Prince Otomo’s Omi court. Rapid marches, strategic river crossings, and local support turned the conflict into a decisive victory.

Tenmu’s forces overwhelmed Otsu’s defenses, and Prince Otomo’s side collapsed in defeat. The victory removed rival claimants and enabled a new regime to punish opponents, reward allies, and reassert imperial command.

He formally took the throne and reestablished rule from the Asuka region, presenting his reign as rightful restoration. Court titles, ranks, and appointments were reorganized to stabilize authority after civil war.

Tenmu promoted Uno no Sarara, a daughter of Emperor Tenji, strengthening legitimacy by uniting rival lineages. Her administrative talent and court network became central to governance and later ensured an orderly succession.

Tenmu emphasized sacred kingship through stricter rites, taboos, and ceremonial discipline tied to kami worship. These measures linked political obedience to religious legitimacy, helping the throne command elites across provinces.

He advanced ritsuryo-style reforms by tightening control over officials, taxes, and regional governance. By clarifying ranks and duties, the court reduced the autonomy of powerful clans and reinforced a bureaucratic state.

Tenmu commissioned the collection of genealogies and court traditions, directing Hieda no Are to memorize authoritative narratives. The project aimed to legitimize the dynasty and became a foundation for later national histories.

The court introduced the Eight Color Cap system to differentiate officials more precisely and reward service. By standardizing hierarchy, Tenmu strengthened centralized command and made advancement depend on imperial favor.

Tenmu died after years of strengthening state institutions, ritual authority, and dynastic narrative. Empress Jito succeeded him, preserving continuity and carrying forward administrative and cultural projects begun under his rule.