The Chōshū Five leave Japan secretly to study at University College London, which is part of the ending of sakoku.

Members of the Chōshū han of western Japan who travel to England in 1863 to study at University College London, the five students are the first of many successive groups of Japanese students who will travel overseas in the late Bakumatsu and early Meiji eras.

All five students will later rise to prominent positions in Japanese political and civil life.

The Chōshū han, based what is now known as Yamaguchi Prefecture, is eager to acquire better knowledge of the western nations and gain access to military technology in order to strengthen the domain in its struggle to overthrow the Tokugawa shogunate.

The decision by Chōshū han elders to sponsor five promising students to study overseas comes in the middle of growing domestic political tensions and in the wake of reports from the First Japanese Embassy to Europe that had returned in January 1863.

At the time of the students departure it us still illegal to leave Japan and travel overseas due to the shogunate's maritime seclusion policy (sakoku or, as it is known at this time, kaikin).

This policy will finally be abolished in 1866.

The Satsuma domain has become closer to the British, despite the bombardment of Kagoshima in 1863, and is pursuing the modernization of its army and navy with their support.

The Scottish dealer Thomas Blake Glover sells quantities of warships and guns to the southern domains.

American and British military experts, usually former officers, may have been directly involved in this military effort.

The British ambassador Harry Smith Parkes supported the anti-Shogunate forces in a drive to establish a legitimate, unified Imperial rule in Japan, and to counter French influence with the Shogunate.

During this period, southern Japanese leaders such as Saigō Takamori of Satsuma, or ...

...Itō Hirobumi and Inoue Kaoru of Chōshū cultivate personal connections with British diplomats, notably Ernest Mason Satow.

The Shogunate also is preparing for further conflict by modernizing its forces.

In line with Parkes' designs, the British, heretofore the Shogunate's primary partner, prove reluctant to provide assistance.

The Tokugawa thus comes to rely mainly on French expertise, comforted by the military prestige of Napoleon III at this time, acquired through his successes in the Crimean War and the War of Italy.

The Shogunate takes major steps towards the construction of a modern and powerful military: a navy with a core of eight steam warships has been built over several years and is already the strongest in Asia.

In 1865, Japan's first modern naval arsenal is built in Yokosuka by the French engineer Léonce Verny.