Military forces around the world have yearned to operate as effectively by night as they do by day. For instance, replenishment of logistics and redeployment of troops may be better conducted under the cover of darkness. Similarly, air strikes are conducted in darkness and at dawn and dusk, to avoid retaliation from enemy interceptors and air defence systems. In addition, it is vital that operational capability should not be limited or hampered by bad weather conditions and long hours of darkness during winter. These operational requirements have motivated the development of night vision devices (NVDs). Today, NVDs can effectively turn night into day. The operational capability of military forces is now extended effectively to cover all 24-hours of a day.