What barriers do you see that would tend to keep an of these river floodplains civilizations fairly isolated and secure from invasion?

Answer 1

River floodplain civilizations often faced natural barriers such as dense vegetation, marshy terrain, and seasonal flooding, making it difficult for invading forces to navigate and mount effective attacks. Additionally, the fertile land and abundant resources provided by the river systems allowed these societies to thrive independently, reducing their need for external interaction. Furthermore, the strategic positioning of settlements near rivers often led to the development of strong defensive structures, enhancing their security against potential invasions.