The Northwest Youth Association (Seobuk Cheongnyeondan) was formed by a group of landowners who were forced to leave North Korea due to the political climate there including land reform and a crackdown on pro-Japanese factions. They were, therefore, naturally hostile to left-wing groups. Having learned that Jeju was the “island of reds,” they saw little wrong in killing Jeju Islanders. Alongside police officers from the mainland, the Northwest Youth Association was deployed to Jeju Island after the shootings on March 1 under orders from the USAMGIK. Although they were given the title of police officers, they were not paid and sustained themselves through the looting of Jeju Islanders.
Taking responsibility for the March 10 general strike, Park Gyeong-hun, the first Jeju governor under the USAMGIK, resigned. His successor, Yoo Hae-jin (1947-1948), assumed the position on April 10, 1947, and it was during his governorship that the first seven members of the Northwest Youth Association arrived on Jeju. From that point until the start of the 4.3 Uprising in 1948, around 760 members of the Northwest Youth Association entered the island. Another 1,700 arrived later. Upon the first arrival, they wore police uniforms before later donning military uniforms.