Goryōkaku was designed in 1855 by Takeda Hisaburō. His plan was based on the work of the French architect Vauban. It is shaped like a five-pointed star. This allowed for greater numbers of gun emplacements on its walls than a traditional Japanese fortress, and reduced the number of blind spots where a cannon could not fire. The fort was built by the Tokugawa shogunate to protect the Tsugaru Strait against a possible invasion by the Russian fleet. Goryōkaku is famous as the site of the last battle of the Boshin War (Goryōkaku no Tatakai). The fighting lasted for a week (June 20–27, 1869).