Western involvement in Boshin War

The Boshin War started because of Meiji Restoration. Losing Opium War, the Western Powers decided to make Japan strong and to be a close ally in East Asia to check Chinese expansion.

The Western Powers selected Meiji government - they hoped that helping him restore the power could make him rely on them.

Background
Japan was in Sengoku before Toyotomi Hideyoshi unified Japan in 1590. Togukawa leyasu defeated Toyotomi loyalists in 1600, and set up Togukawa Shogunate in 1603, later conquered entire Japan in 1615, and ruled for over 200 years.

1853, American fleet arrived at Japan, forcing them to open up. Ansei Treaties was signed later, hoping not to make Japan become a semi-colony, Meiji Emperor made the Charter Oath, which was an icon of the start of Meiji Restoration.

The restoration was a disaster for the Daimyo, which made some of them, with Togukawa loyalists, battled against the Meiji government. To restore power, Meiji Emperor must defeat them since they were the real ruler of Japan. Boshin War then started.

Western involvement
The Western Power, mainly France and Britain, landed in Tokyo, when the two Japanese camps were fighting nearby. Tokyo fell within a month, and later retreated to Hokkaido, continued fighting Meiji government, but soon failed. Meiji government, seeing how powerful Western Army was, learnt from them and quickly became a modern nation.

Western's wish
Western Powers expected Japan to rely on them, but failed since Japan did their own reform. The Western Power even wished Japan to transfer into their semi-protectorate which would listen to them. Although Japan listened to them, Japanese government wished not to totally depend on them. Japanese Empire would soon have conflicts with Western Power, or China, since they had noticed, Japan was too small for them.

Consequence

 * Battle of Sakhalin Island