Passage: The Gombe Chimpanzee War (also known as the "Four-Year War" of Gombe), lasting from 1974 to 1978, was a violent conflict between two communities of chimpanzees in Gombe Stream National Park, in Tanzania. The belligerent groups were the Kasakela and the Kahama, which occupied territories in the northern and southern areas of the park, respectively. The two had previously been a single, unified community, but by 1974 researcher Jane Goodall, who was observing the community, first noticed the chimps dividing themselves into northern and southern sub-groups. Later computer-aided analysis of Goodall's notes would reveal that the social rift between the two groups had been present as early as 1971.The Kahama group, in the south, consisted of six adult males (among them the chimpanzees known to Goodall as "Hugh", "Charlie", and "Goliath"), three adult females and their young, and an adolescent male (known as "Sniff"). The larger Kasakela group, meanwhile, consisted of twelve adult females and their young, and eight adult males.

Question: In what years did the Gombe Chimpanzee war take place?
1974 to 1978