Imminent civil war and the mobilization of armies

Imminent civil war and the mobilization of armies is the widening crisis in which Toranaga and Ishido’s contest for power hardens into a military confrontation. The conflict grows from the unstable regency and the disputed control of the Heir into a struggle over roads, fortresses, weapons, and the timing of battle. Its defining reversal is Toranaga’s decision to attack first: after maneuvering to gain time, he orders Crimson Sky and begins moving armies toward the Tokaidō.

Succession, hostages, and the approach of war

The political crisis rests on the Taikō’s succession arrangements. After his death, five Regents were to rule during the minority of his son, Heir Yaemon, who was seven. Toranaga and Ishido possessed the real power among the Regents, and their rivalry gave the formal council’s rules immediate military significance. Toranaga’s position in Osaka was precarious: while he was away, friendly neighboring daimyos had been invited to wait in Yedo, where they and their families effectively served as hostages to secure his safe return from Ishido’s stronghold.

Hostage-taking also exposed the gap between the Taikō’s covenants and the Regents’ conduct. Ishido argued that Toranaga’s keeping Lady Ochiba, the Heir’s mother, in Yedo violated the prohibition against Regents holding one another’s hostages. Toranaga presented her presence as a family visit to her sister, who was married to his son and heir. Ishido nevertheless demanded that she return. The dispute made family ties and the Heir’s safety instruments in the same political contest as armies and fortifications.

As Toranaga prepared for the final confrontation, he anticipated that Ishido and his allies would move against him. He expected to be outnumbered by at least three to one and reasoned that victory would depend on the time and place of battle, not simply the size of the forces. His calculations included the prospect that Ishido would be drawn out of Osaka Castle. In the chess-like contest, Toranaga understood Mariko’s sacrifice as a costly move that had nevertheless weakened Ishido’s position. The coming war was therefore shaped by political acts as well as troop strength: a sacrifice could change where an opponent was able to act.

Firearms and a changed battlefield

The military crisis also tests the inherited standards of samurai warfare. Muskets and gunpowder had reached Japan through the Portuguese; within eighteen months, Japanese makers were producing firearms, although their quality did not match European weapons. Guns initially remained a novelty, used chiefly for hunting, while bows were considered more accurate. More profoundly, ritualized, individual hand-to-hand combat made the sword the honorable weapon. Firearms were associated with cowardice and dishonor, in tension with Bushido’s demands of honorable fighting, fearless death, and unquestioning service to one’s lord.

Yabu had privately considered how to make that discredited weapon decisive. When the captured ship’s cargo revealed five hundred muskets, abundant powder and shot, twenty cannon, thousands of cannonballs, and crates of fire arrows, he ordered the armament moved secretly to his castle at Mishima. He envisioned five hundred selected samurai, armed and trained to fight as one unit, advancing before twelve thousand conventional troops. Twenty cannon, operated by specially trained men, would support them. The weapons were not merely a windfall: in Yabu’s view, they offered a strategy for a new era and a possible advantage in the war to come. His question about what the plan meant for Bushido remained unresolved; the old code and the new method stood in direct tension.

A later demonstration gave that tactical theory visible form. The attackers divided into five disciplined phalanxes, each four ranks deep, with three units forward and two held in reserve. They fired by ranks: the front knelt to reload while successive lines shot over them. When the defenders counterattacked, the formations appeared to break and flee, then regrouped in a V and resumed their volleys. The demonstration used blank ammunition and staged casualties, but its implication was clear to the observers: under real conditions, the defending force would have been overwhelmed. The exercise made coordination, repeated fire, and disciplined withdrawal—not individual prowess alone—the measure of battlefield power.

Fortresses, roads, and the limits on movement

The geography of the crisis imposed its own military logic. Osaka Castle was not a single wall that an army could overcome in one assault. Its enormous gates, deep moats, bridges, successive walls, and guarded approaches formed layers of defense. Beyond one gate, roads twisted past fortified houses and other checkpoints until even an exceptionally observant visitor lost his sense of direction. Gray-uniformed soldiers watched from ramparts and bastions, while others guarded, marched, trained, or tended horses. The castle’s depth helped explain why political opponents could be trapped within it and why an escape or relief force had to be planned around controlled passage as much as fighting.

At the wharf, Toranaga and Yabu studied a galley held near a detachment of a hundred Gray soldiers. A wide stretch of open ground between the alley and the gangway made a surprise attack difficult. When Yabu proposed setting fire to the street as a diversion, a samurai protested that arson brought the public burning of the guilty person’s entire family, across generations. The law reflected the danger of fire in a city built largely of wood and paper; it also made the proposed tactic a grave sacrifice imposed on others. Yabu’s counterargument reduced the choice to the destruction of a few streets or the death of their lord. The episode shows how the emergency pressed military decisions against legal prohibitions and the safety of civilians.

From delay to Crimson Sky

Toranaga’s response combined deception, preparation, and a deliberate choice of timing. He arranged for the courtier Ogaki Takamoto to tell Ishido that the Emperor’s visit to Osaka had to be delayed because of ill health. Ogaki was a descendant of the Imperial line but impoverished, since the Imperial Court had no independent revenue; Toranaga had secretly assigned him an annual stipend of ten thousand koku through intermediaries. He hoped the Emperor or his advisers would welcome a reason to postpone or cancel the visit. Toranaga knew that such an intervention could be construed as treason, but he was already indicted on that charge. The maneuver sought to disrupt Ishido’s timetable even as it increased the political stakes.

The delay could not prevent the armies from committing themselves. Toranaga received word that Ishido and the Heir had left Osaka to review the armies and concluded that the conflict was now unavoidable. He ordered the Musket Regiment to Hakoné at dawn and made preparations for the baggage train from Yedo. When he learned of Jikkyu’s death—information he had received advance warning of through Kasigi Mizuno—he ordered four regiments at Mishima onto immediate alert, to be sent down the Tokaidō in four days. Sudara recognized the order as Crimson Sky and asked whether Toranaga was attacking. Toranaga answered that he would not wait for the enemy to come against him.

The operational plan extended beyond the first strike. Toranaga directed Sudara to Mishima to prepare everything, while Hiro-matsu’s assault force was allotted twenty days to cross the Tenryu River and secure the Tokaidō Road. Sudara proposed allowing thirty days and advancing as far as the crest of the Shiomi Slope. Toranaga refused: an order to reach the crest would leave most of the force dead and unable to repel a counterattack or harass the enemy during retreat. The exchange defines the campaign’s hard arithmetic. The objective was not simply to advance as far as possible, but to preserve enough men to make the next movement survivable.

By the time Crimson Sky was ordered, civil war was no longer a distant threat. Ishido’s review of the armies, Toranaga’s deployment orders, the regiments’ movement toward the road, and the careful allocation of time to Hiro-matsu’s force made the confrontation concrete. Yet neither numbers nor weapons alone guaranteed victory. Toranaga’s plans depended on controlling when the enemy moved, where the armies met, and what forces remained after the first assault. The mobilization turns the succession struggle into a contest of military systems and political timing, with the older language of loyalty and honor tested by firearms, deception, and the calculated cost of survival.