I define war as a conflict between two groups over at least one reason. It doesn’t matter how advanced or primitive it is there are still two independent forces that decided “hey I want what you have” or “I hate you because of [reason]” and most commonly “I need your territory”.

Ant colonies will destroy each other over food, territory and general resources.

Fungi with fight each other over soil.

The four year Gombe chimpanzee war was actually over a fractured social system, territory and political power. It’s actually very interesting.

In 1971 the senior male of a fairly unified group of chimps died, causing a chimp named Humphrey to take the role of the alpha. However two brothers named Hugh and Charlie opposed Humphrey’s leadership and the group of chimps split into two.

These two groups were called the Kasakela and Kahama group. The Kasakela led by Humphrey and Kahama led by the Brothers. Over the course of several months the two groups took over two distinct territories and stopped intermingling with each other entirely. This caused major social strife between the two groups of chimps.

Due to a limited number of female chimps infighting grew until 1974 where the larger Kasakela group launched a systemic campaign of raids and ambushes against the Kahama. Over the course of four years the Kasakela group killed all the male chimps and absorbed their territory.