The incident was a provocation premeditated by Japan to invent an excuse of its armed invasion of Korea.

After "the 1868 Meiji Restoration", Japan brought up "theory of the conquest of Korea" in a bid to secure huge funds needed for consolidating a foundation of capitalism and building "a wealthy country with a powerful army" through aggression on Korea.

To this end, it stepped up the preparations for aggression on Korea and masterminded "Unyo-maru" incident.

In May 1875, three warships of Japan including "Unyo-maru" sailed into the coastal waters of East and South Seas of Korea to perpetrate espionage and bombardment under the pretext of firing training.

In September that year, the "Unyo-maru" intruded into the waters off Kanghwa Island in the Weat Sea of Korea under the pretext of surveying sea route. On the plea of "finding drinking water" on September 20, the warship approached close to the Chojijin fortress in Kanghwa Island, a point of military importance in the West Sea of Korea.

So, the guards of the fortress took punitive action against it. Availing themselves of this action, the Japanese invaders fired guns to the fortress and turned other islands of Korea with weak defensive power into ashes.

In order to conceal the truth of criminal "Unyo-maru" incident, Japan shifted all the blames on to the Korean feudal government and militarily forced the latter to conclude a "treaty" under the veil of exacting "apology" and "reparation".

After all, "Kanghwa Island Treaty", a subordinate and unequal treaty, came into being in February next year.

As seen above, the "Unyo-maru" incident provoked by Japan was aimed to make a "legal basis" for subjugating Korea through the coerced conclusion of an unequal treaty.