Why would economic scarcity often lead to increased warfare between two farming communities

Scarcity often leads to warfare because it supports people to survive.

Explanation:

Lack of food would make people hostile, and a food search will begin to become flourish as they were before. The two communities will fight to gain power and get access to grains as a source of food for survival. Men will turn into fighters who will lead wars towards vulnerable farming communities. As cities began to establish, there was a demand for the supply of grains in these cities where people occupied in a different occupation which had nothing to do with agriculture. As cities grew, they needed a large quantity of food.

i believe it was the shinto