In fact, it is a tradition of the US military to accidentally injure friendly troops. On the battlefield of World War II, it seems that more than 1000 American soldiers were accidentally injured by friendly forces. With the development of weapons of mass destruction, many American troops were hit by friendly shells or bullets in the jungles of Vietnam. On the Korean battlefield, the American army, as the big brother of the United Nations army, did not kill the allies. In fact, friendly fire has always been a headache for armies of all countries. This data was even exaggerated during the Gulf War. According to the data leaked by the US military, in the Gulf War, more than 20% of the wounded were accidentally injured by friendly forces. This is enough to show the importance of IFF system.
It is very complicated to distinguish between the enemy and ourselves on the battlefield, because people are highly nervous. When they find moving objects, their instinctive reaction is to shoot. Therefore, in order to enable soldiers to quickly distinguish between the enemy and ourselves, the military uniforms of different countries are often different. But sometimes, the uniforms of the two armies are similar, which is even more difficult to do on the battlefield. Remember that episode in "Bright Sword"? Soldiers from both sides met while smoking and even borrowed a light. It was not until the soldier put on his helmet that he found himself an enemy soldier. Then the two sides began a scuffle.
Although military uniforms can be identified quickly, it is easy for the enemy to obtain our military uniforms. So another way for the army is to correct slogans. But it can be used in your own station, not behind enemy lines. So the US military developed the cricket whistle, that is, in Brothers, Captain Winster parachuted behind the enemy and used the cricket whistle to make a sound to judge whether the shadow in front was his own army. If the other party responds, he starts asking for the password. Because the sound of cricket also exists in nature, it is easy to confuse the enemy.
But as I said just now, the sound of cricket also exists in nature, so it is easy to cause interference. What about these? Weird skills and cunning Can't be used for frontal battlefield. Therefore, at the end of the 20th century and the beginning of the 20th century, when American military aircraft and artillery provided support to friendly forces, they all asked friendly forces to indicate their targets with smoke bombs or lasers. Moreover, it is necessary to repeatedly confirm the position of friendly forces before the attack. However, at that time, the US military did not cultivate the ability of multi-arms to cooperate, so many people were accidentally injured by friendly forces because of improper scheduling and chaotic command.
With the development of science and technology. The us military began to distribute a large number of identification equipment for its own troops. Because of its huge size, the equipment can only be used in vehicles at first. But now the IFF system can be equipped by individual soldiers. With this system, soldiers don't have to worry about being patronized by friendly planes when requesting support.