Japan's rainy season

Japan's rainy season is both a seasonal obstacle and a strategic clock in the novel: its expected duration gives Ishido time to prepare a campaign, while its difficult conditions make Toranaga's decision to attack before it ends a startling reversal. The rains turn the question of when to fight into a contest over who can use delay, terrain, and surprise to best advantage.

Duration and Strategic Setting

Omi estimates that the rains will continue for about two months. Until they stop, he expects Ishido to hold back from a major assault; afterward, Ishido could send Ikawa Jikkyu and Lord Zataki against Toranaga in a pincer movement, supported by Ishido's main army advancing along the Tokaido.

Omi also sees the season as a period of political uncertainty. While Ishido waits, daimyo with grievances against one another may pay him only lip service, then pursue revenge or seize territory when he makes his first move. In Omi's forecast, the resulting disorder could tear the Empire apart as it had been before the Taikō. Toranaga and Yabu might meanwhile hold the passes to Kwanto and Izu against the first attack, preserving their strength until their rivals had exhausted themselves.

The Case for Waiting

Omi's advice is to remain behind the mountains, tighten security, and keep the musket regiment out of action. He regards it as a secret weapon to preserve for a later opportunity, when Toranaga has gathered more allies. In this plan, the rains are protective: they defer the decisive clash while Toranaga strengthens his position and waits for Ishido's coalition to weaken.

Naga offers a different use for the same interval. Rather than wait until the rains cease, he proposes using the two months to gather allies and isolate Ishido further, then attacking without warning when the season ends. His proposal retains the advantage of preparation but refuses Omi's longer defensive timetable.

Toranaga's Decision

Toranaga rejects both the expectation of a prolonged defensive wait and the assumption that the army must postpone action until the weather improves. He declares that the forces will go to war at once. When the rainy-season difficulty is raised, he accepts that his troops will reach Kyoto wet, hot, and stinking, and argues that surprise, mobility, audacity, and timing can win wars. He also says the guns will blast a way through the mountains.

The decision is presented as an unheard-of strategy: Toranaga spends an hour discussing the feasibility of large-scale warfare during the rains before sending the others away. The weather remains a real cost, not a difficulty that has disappeared; his gamble is that speed and the shock of an unexpected campaign will outweigh it.

Narrative and Military Significance

The rainy season gives the military situation a deadline, but not a fixed rule for action. Omi reads it as a reason to wait and conserve a secret weapon; Toranaga turns it into a test of initiative, choosing to make the opponent respond before the anticipated conditions for war have arrived. The contrast reveals how the same terrain and weather can support opposing strategies: mountain passes can shelter a force, yet guns and a sudden advance can make those barriers part of an offensive plan.

By choosing to fight in the rains, Toranaga overturns the timetable that his advisers have been discussing. The season therefore marks a shift from calculating how long his side can safely defer battle to attempting to seize the moment before Ishido can act on his own plans.