Early civilizations were likely to fight over numerous things, as back then things were very scarce.
The thing that is most likely to have caused fights among the early civilizations would be resources. Like I stated before, resources were scarce. People had to do everything by hand, make weapons, catch food, make their own homes, so items that were needed to obtain these things, were often fought about, this includes the easy access of water.
Another huge thing would be land. Certain parts of land came with an abundance of goods, like animals, fruits, trees, and water. This caused fights among land and who would own parts of land.
Culture was also another aspect that caused wars. Culture and religion and the spread of it, often caused fights and wars among the early civilizations, as they normally did not accept other point of views and opinions.
Control of trade and increasing trade is another reason for the early civilizations to fight. Control of trade was very important, as whoever controlled the trade made the most money and would obtain the most goods.
