1, the internal political struggle in the city season is fierce, and the groups that failed in the struggle have moved out because it is difficult to gain a foothold in the city-state.
At that time, industry and commerce were relatively developed. Industrial and commercial slave owners are very active. In order to seek more sources of raw materials and slaves, they found another way to establish commercial strongholds in other places. Their commercial strongholds gradually formed city-states.
There is a serious polarization between the rich and the poor in society. In the process of polarization between the rich and the poor, indebted farmers have to flow out one after another in order to make a living.
4. "The pressure of surplus population on productivity". Within the narrow city-state, the level of productivity development at that time could not meet the needs of more people. "The only way out is forced immigration." For example, in the late 7th century BC, there was a severe drought in Tello Island, and there was no rain for seven years, so residents were forced to draw lots to choose one of the two brothers to colonize Culene in Leah.