What is the Terminal High Altitude Area Defense System (Thaad)?
© Getty Images The exercises generate tensions every year, but this year come at an extremely sensitive time
Shoots down short and medium-range ballistic missiles in the terminal phase of their flight
Uses hit-to-kill technology - where kinetic energy destroys the incoming warhead
Has a range of 200km and can reach an altitude of 150km
US has previously deployed it in Guam and Hawaii as a measure against potential attacks from North Korea