The Chimpanzee War, 1974-1978

Sometimes earth-shattering events go on right under our noses, and we pay no attention to them because we are human. We most likely would have no knowledge at all of a war going on for years in Nigeria if Jane Goodall hadn't been there to document the Gombe Chimpanzee War. She was there at the Gombe Stream National Park in 1974 when a war broke out between communities of chimpanzees. One population started to infringe on the territory of another, and they fought over it until 1978.

During the war, male chimps were observed forming alliances, sharing patrol duties, and carrying out raids and attacks that indicated strategic planning. Read about the human-like war and the implications of such behavior among chimpanzees at History of Yesterday. 
But that article didn't tell us how the war ended, or who won. Wikipedia has a longer and more detailed account of the war, and Goodall's reaction to it.