Defense (THAAD) is a land-based theater anti-missile system under the U.S. Missile Defense Agency and the U.S. Army, collectively known as the Sade anti-missile system.

After the Gulf War, the MIM- 104 air defense missile used by the United States in the war belongs to low-altitude air defense missile, with the maximum launching height of only about 20 kilometers, which is mainly used to protect small and important targets. The defense area is small, and the interception is not carried out in a high enough space. Moreover, missile fragments caused by interception often fall on the territory of their own countries or friendly countries, which will also cause damage to people and assets on the ground. If the enemy uses weapons of mass destruction, such as nuclear warheads and chemical warheads, low-altitude interception like this has little effect. Therefore, it is necessary to develop a high-tech technology that can intercept incoming ballistic missiles at a longer distance and at a higher altitude. 1987, the us army space and strategic defense command put forward the development plan of high-altitude defense technology for theater ballistic missile defense.