Final answer:
Difficult ground is often assigned as an objective in military operations as it provides the enemy with effective observation along a friendly axis of attack and ensures the required destruction of threat forces.
Step-by-step explanation:
The terrain described in the question is often assigned as an objective in military operations. It is referred to as difficult ground and includes features such as mountain forests, rugged steeps, marshes, and fens that are hard to traverse. This type of terrain is strategically important because it can provide the enemy with effective observation along a friendly axis of attack and ensure the required destruction of threat forces.