The Jeju Uprising started during the U.S. occupation period in April 1948 when left wing radicals killed 30 South Korean police officers. This uprising happened after a South Korean communist named Pak Hon-yong (who collaborated with Kim Il-sung in Pyongyang) called on left wing and communist groups south of the 38th parallel to oppose the 1948 Korean elections by whatever means necessary, and called for a general strike to begin on 7 February. At this point, there were at least 60,000 members of the communist Workers' Party of South Korea on Jeju, and at least 80,000 active supporters. These members and supporters not only went on strike but in some cases attacked government installations and engaged with police forces in open conflict. These engagements between SKLP guerrillas against rightist groups and police continued through March 1948. It was a brutal war for the next 13 months that resulted in atrocities by both sides that led to the deaths of 60,000-100,000 people.