Jeju uprising to Jeju from Busan and deploying police companies, each 1,700 strong, from the southern provinces of the mainland. The guerrillas retreated to their bases in the forests and caves around Hallasan, an extinct volcano and the highest mountain in South Korea. On April 29, the Korean, non-military, governor of Jeju province abandoned his post, defected, and joined the guerrillas. This caused many police officers, disillusioned by the atrocities they were ordered to commit against their own, to do the same. In response, U.S. military provincial governor William F. Dean ordered a purge of SKLP sympathizers from the ranks of the
Hallasan in Jeju Island and 6 of them can be found in the natural reserve area of Hallasan. Also, about 50 kinds of special plants are distributed in Jeju Island, especially in the highlands of Hallasan. Because of the geographical character of the island, there are many subspecies due to isolation even though they are the same species. Also, Hallasan is a place where the polar animal and the tropical animal coexist due to the difference of the climate zone according to the elevation. The mammals of Jeju Island are distributed among 5 orders and 114 families and 5 species .