The HMS Actaeon was a British warship which called at Tsushima han and Pusan several times in 1859. Historian Robert Hellyer identifies their visit as marking "the beginning of a new phase of Western intrusion [in and around Tsushima]," in which captains of Western ships began to consider a desire to establish bases on Tsushima.
The Actaeon was perhaps the first Western ship whose crew made landfall in a significant way, staying on the island for days, on several occasions. However, it was hardly the first Western ship to pass by Tsushima; officials reported tens upon tens of sightings of Western ships in the late 1840s to early 1850s, sometimes tens of sightings within just a one or two week period.
The Actaeon first arrived at Tsushima in the fourth month of 1859. Its crew remained at the island for three weeks, visiting a number of coastal villages, and climbing Mt. Shiratake. They then traveled to Pusan, where they charted the harbor and sent representatives to the Waegwan (the Tsushima residence in Korea). Tsushima then dispatched an additional ten men to bolster defenses at the Waegwan.
The Actaeon returned later in the year, spending around one week at Pusan, and one at Tsushima, in the tenth and eleventh months.
In response to these incidents, Tsushima petitioned the shogunate to ban foreign ships from calling at Tsushima, but in accordance with the Harris Treaty signed the previous year, Western ships were permitted to call at any Japanese ports, so long as they were in need of supplies or of aid otherwise, and so long as they did not stay too long.
- Robert Hellyer, Defining Engagement, Harvard University Press (2009), 173-176.