What are some of the typical reasons why empires and dynasties tend to decline and fall?

Empires and dynasties tend to hold power for a given period of time, after which they naturally collapse due to different reasons.

First, they usually start to debilitate due to fatigue and languishment. People ruled by a dynasty or empire, after a long period of time, tend to get tired from the control exercised by the same rulers. In the same way, the dynasties and empires get old and the resources they used in the past to hold power lost their originality. This is why they tend to decline.

Second, this fatigue and lack of originality are taken as an advantage by new groups that try to concentrate power and defy the ruling dynasty or empire, in order to overturn them. For these reasons, empires and dynasties tend to decline and fall.

c. troops marched forward in close formation against newer, more accurate weapons