Kagoshima Bay
At the time, Nagasaki was the only point of contact between Japan and the Western nations due to the Tokugawa shogunate's national isolation policy. Takashima was shocked to find the difference between Japanese and Western technology, especially in terms of weapons. Takashima set up an artillery foundry at his own expense based on Dutch designs in 1834, and present a bronze mortar to Nabeshima Shigeyoshi, "daimyō" of Saga Domain in 1835. Various domains sent students to learn from Takashima. They included samurai from Satsuma Domain after the intrusion of an American warship in 1837 in Kagoshima Bay, and from Saga Domain and Chōshū Domain, both southern domains exposed to Western intrusions.