Shōzan Proposes Eight Measures for Coastal Defense

By 1842, Sanada Yukitsura held responsibility for coastal defense in the shogunate, and Sakuma Shōzan supplied advice from the Matsushiro domain. In the eleventh month, Shōzan presented eight measures later known as the Kaibō hassaku. Study of foreign knowledge gave the proposal specific technical content.

He called for batteries at strategic coastal sites and for copper otherwise exported through Dutch trade to be used for cannons. Stronger Western-style vessels would protect transport as well as support defense; warships required trained crews and suitable officers. Other points proposed village schools, clear rewards and punishments, and the selection of capable men for service. Military equipment and administration therefore belonged to the same program.

Shōzan pursued artillery study with Egawa Tarōzaemon and drew on other scholars’ knowledge. These connections helped make his advice more than a general warning about foreigners. The eight measures remained proposals addressed to an existing government: schools and recruitment were framed through loyalty, discipline and lordly authority. Their submission does not establish that the shogunate adopted the full program in 1842.