[1] Keangsoo was a wooden dispatch vessel, laid down at Whites' shipyard at Cowes on the Isle of Wight in 1862 and launched on March 5, 1863.

Prince Gong of the Qing Dynasty gave permission for Lay to proceed with this task, and provided the funds to procure the ships.

While some, such as HMS Africa (subsequently renamed China) were purchased from the Royal Navy, Keangsoo was one of three dispatch vessels alongside Tientsin and Kwangtung which were procured as new builds.

Following the intervention of a British minister,[5] the fleet was ordered to depart for India with Osborn taking Keangsoo, Kwangtung, Amoy and the yacht Thule to Bombay (now Mumbai).

The Keangsoo was then laid up alongside the other remaining vessels of the flotilla, since their sales were embargoed until the end of the American Civil War.

[3] While at Nagasaki, Keangsoo was purchased by Matsukata Masayoshi, a leading Satsuma samurai, on November 3, 1867, for the amount of 160,000 ryō (approx $250,000 at then current exchange rates), whence she was renamed Kasuga Maru.

In March 1869, Kasuga Maru participated in the expedition against the last remnants of the pro-Tokugawa forces in Hokkaido, where they had formed the Republic of Ezo with the support of a few French military advisors such as Jules Brunet.

After these events Kasuga Maru participated in the Naval Battle of Hakodate Bay in May 1869, until the surrender of the last forces of the Republic of Ezo.

The failure of this mission was one of the underlying factors in the subsequent Ganghwa Island incident of 1875, during which Kasuga was assigned to blockade the port of Busan.