Second Chōshū expedition

Second Chōshū expedition 第二次長州征討
Part of Bakumatsu Conflicts
Operations map of the Second Chōshū expedition.
Date 7 June 1866 Location Western Japan Result Decisive Shogunal defeat
Belligerents
Chōshū Domain	Tokugawa shogunate Aizu Domain Fukuyama Domain Hamada Domain Higo Domain Hikone Domain Iyo-Matsuyama Domain Karatsu Domain Kishū Domain Kokura Domain Kurume Domain Kuwana Domain Ōgaki Domain Nakatsu Domain Takada Domain Yanagawa Domain
Strength
3,500-4,000	100,000-150,000
Casualties and losses
261 killed	unknown

Tokugawa shogunate
Aizu Domain

The Second Chōshū expedition (Japanese:第二次長州征討), also called the Summer War, was a punitive expedition led by the Tokugawa shogunate against the Chōshū Domain. It followed the First Chōshū expedition of 1864.

The Second Chōshū expedition was announced on 6 March 1865. The operation started on 7 June 1866 with the bombardment of Suō-Ōshima in Yamaguchi Prefecture by the Navy of the Bakufu.

The expedition ended in military disaster for the shogunate troops, as Chōshū forces were modernized and organised effectively. By contrast, the shogunate army was composed of antiquated feudal forces from the Bakufu and numerous neighbouring domains, with only small elements of modernised units. Many domains put up only half-hearted efforts, and several outright refused shogunate orders to attack, notably Satsuma who had by this point entered into an alliance with Chōshū.

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