In the wake of these failed peace negotiations, the fighting continued. The U.S. military government responded to guerrilla activity by transferring another regiment 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 29 April, 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 Korean Constabulary, and three sergeants were summarily executed.: