Military fortifications can be (exclude unnecess ary ones): long-tern and field natural and artificial open and closed type

The correct answer is: natural and artificial.<br /><br />Military fortifications can be classified as or artificial. Natural fortifications refer to geographical features such as mountains, rivers, and coastlines that provide natural defense and protection. These features can be utilized by military forces to establish defensive positions and control access to certain areas.<br /><br />On the other hand, artificial fortifications are man-made structures designed specifically for military purposes. These structures can include walls, trenches, bunkers, and other defensive installations constructed to enhance the security and strategic capabilities of a military force. Artificial fortifications are built to withstand enemy attacks and provide cover and protection to troops and equipment.<br /><br />It is important to note that the classification of military fortifications as natural or artificial does not imply that one is superior to the other. Both types of fortifications have their own advantages and can be effectively utilized in different military scenarios.