What type of existing obstacles is considered natural?

Rivers are classified as natural obstacles because they are formed by geological processes and exist in the environment without human intervention. Their physical characteristics can impede movement and influence operational planning, making them significant when assessing terrain.

In contrast, fortifications, barbed wire, and minefields are human-made obstacles. Fortifications are constructed defenses meant to protect an area or position; barbed wire is utilized to deter movement or entry into an area; and minefields are deliberately laid to disrupt or destroy enemy forces. These man-made obstacles are designed to influence battle spaces strategically, while rivers naturally alter the landscape and create challenges that must be navigated or accounted for during operations. This distinction emphasizes the importance of understanding the different types of obstacles in military planning and tactics.