Dharma Initiative
When the Dharma Initiative arrived on the Island, they fought with the Island's natives, known to them as the Hostiles and to the survivors of Flight 815 as the "Others". The "Hostiles" had been living on the Island long before the Initiative arrived. The Arrow Station was eventually given a mission to observe and formulate strategies to counter the Hostiles. When Ben Linus (Michael Emerson) arrived on the Island in 1970, there was still an open conflict between the Hostiles and the Dharma Initiative. At some point prior to 1974, a truce of some kind was brokered with the Hostiles. A series of protocols were put into place between the Hostiles and the Initiative. Several episodes mention that there was a "line" and that certain parts of the Island were considered to be the "territory" of each group. This conflict ended in 1992, when Linus joined the Hostiles, who killed the Initiative, an event which became known as "The Purge". The bodies were buried in a mass grave.