在交战时期,有效地阻止敌人进攻比对一个既成事实的战术反应更为需要。在战场上为了制止敌人的行动自由和阻止敌方人员、物资的补给,需要准确地确定其位置,以及对敌方运动提供预警。通常这些信息是通过各种各样的侦察飞机来获取的。然而由于战场被地面上的天然植被、地物、甚至敌人的伪装物所掩盖,因此不能用侦察机对目标进行探测。 上述考虑在六十年代后期才提到议事日程上来。当时东南亚的美军发现了北越共产党所 In warring times, it is even more necessary to stop the enemy from attacking more effectively than a tactical response to a fait accompli. On the battlefield, in order to stop the enemy’s freedom of movement and prevent enemy personnel and supplies from relying on supplies, they need to accurately determine their position and provide early warning of enemy movements. Usually this information is obtained through a variety of reconnaissance aircraft. However, the target can not be detected by reconnaissance plane because the battlefield is covered up by natural vegetation, terrain and even enemy camouflage on the ground. The above considerations did not refer to the agenda until the late 1960s. At that time, the U.S. forces in Southeast Asia discovered the North Vietnamese Communist Party